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circulation</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. 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href="https://et.wikipedia.org/wiki/Loote_vereringe" title="Loote vereringe – Estonian" lang="et" hreflang="et" data-title="Loote vereringe" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Circulaci%C3%B3n_fetal" title="Circulación fetal – Spanish" lang="es" hreflang="es" data-title="Circulación fetal" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Jaio_aurreko_zirkulazio" title="Jaio aurreko zirkulazio – Basque" lang="eu" hreflang="eu" data-title="Jaio aurreko zirkulazio" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Circulation_f%C5%93tale" title="Circulation fœtale – French" lang="fr" hreflang="fr" data-title="Circulation fœtale" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%83%9C%EC%95%84%EC%88%9C%ED%99%98" title="태아순환 – Korean" lang="ko" hreflang="ko" data-title="태아순환" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8A%D5%BF%D5%B2%D5%AB_%D5%A1%D6%80%D5%B5%D5%A1%D5%B6_%D5%B7%D6%80%D5%BB%D5%A1%D5%B6%D5%A1%D5%BC%D5%B8%D6%82%D5%A9%D5%B5%D5%B8%D6%82%D5%B6" title="Պտղի արյան շրջանառություն – Armenian" lang="hy" hreflang="hy" data-title="Պտղի արյան շրջանառություն" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Fetalni_krvotok" title="Fetalni krvotok – Croatian" lang="hr" hreflang="hr" data-title="Fetalni krvotok" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Circolazione_nei_vivipari" title="Circolazione nei vivipari – Italian" lang="it" hreflang="it" data-title="Circolazione nei vivipari" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%97%E0%B5%BC%E0%B4%AD%E0%B4%B8%E0%B5%8D%E0%B4%A5%E0%B4%B6%E0%B4%BF%E0%B4%B6%E0%B5%81%E0%B4%B5%E0%B4%BF%E0%B4%A8%E0%B5%8D%E0%B4%B1%E0%B5%86_%E0%B4%B0%E0%B4%95%E0%B5%8D%E0%B4%A4%E0%B4%9A%E0%B4%82%E0%B4%95%E0%B5%8D%E0%B4%B0%E0%B4%AE%E0%B4%A3%E0%B4%82" title="ഗർഭസ്ഥശിശുവിന്റെ രക്തചംക്രമണം – Malayalam" lang="ml" hreflang="ml" data-title="ഗർഭസ്ഥശിശുവിന്റെ രക്തചംക്രമണം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Foetale_bloedsomloop" title="Foetale bloedsomloop – Dutch" lang="nl" hreflang="nl" data-title="Foetale bloedsomloop" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a 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searchaux" style="display:none">Circulatory system of fetuses</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox"><tbody><tr><th colspan="2" class="infobox-above" style="background-color:thistle">Fetal circulation</th></tr><tr><td colspan="2" class="infobox-image"><span typeof="mw:File"><a href="/wiki/File:2916_Fetal_Circulatory_System-02.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/2916_Fetal_Circulatory_System-02.jpg/300px-2916_Fetal_Circulatory_System-02.jpg" decoding="async" width="300" height="261" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/2916_Fetal_Circulatory_System-02.jpg/450px-2916_Fetal_Circulatory_System-02.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/be/2916_Fetal_Circulatory_System-02.jpg/600px-2916_Fetal_Circulatory_System-02.jpg 2x" data-file-width="2235" data-file-height="1948" /></a></span><div class="infobox-caption">The fetal circulatory system includes three shunts to divert blood from undeveloped and partially functioning organs, as well as blood supply to and from the placenta.</div></td></tr><tr><th colspan="2" class="infobox-header" style="background-color: #efefef">Details</th></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Embryology" title="Embryology">Gives rise to</a></th><td class="infobox-data"><a href="/wiki/Circulatory_system" title="Circulatory system">Circulatory system</a></td></tr><tr><td colspan="2" class="infobox-below"><a href="/wiki/Anatomical_terminology" title="Anatomical terminology">Anatomical terminology</a><div style="text-align: right;"><small class="noprint">[<a href="https://www.wikidata.org/wiki/Q2657962" class="extiw" title="d:Q2657962">edit on Wikidata</a>]</small></div></td></tr></tbody></table><p>In humans, the <a href="/wiki/Circulatory_system" title="Circulatory system">circulatory system</a> is different before and after birth. The <b>fetal circulation</b> is composed of the <a href="/wiki/Placenta" title="Placenta">placenta</a>, umbilical blood vessels encapsulated by the <a href="/wiki/Umbilical_cord" title="Umbilical cord">umbilical cord</a>, heart and systemic <a href="/wiki/Blood_vessel" title="Blood vessel">blood vessels</a>. A major difference between the fetal circulation and postnatal circulation is that the lungs are not used during the fetal stage resulting in the presence of shunts to move oxygenated blood and nutrients from the placenta to the fetal tissue. 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system</a></li><li><a href="/wiki/Development_of_the_reproductive_system" title="Development of the reproductive system">Reproductive system</a></li><li><a href="/wiki/Development_of_the_urinary_system" title="Development of the urinary system">Urinary system</a></li><li><a href="/wiki/Development_of_the_endocrine_system" title="Development of the endocrine system">Endocrine system</a></li><li><a href="/wiki/Development_of_the_human_body" title="Development of the human body">Human development</a></li><li><a class="mw-selflink selflink">Circulatory system</a></li></ul></div></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar 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href="/wiki/Template:Organ_system_development" title="Template:Organ system development"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Organ_system_development" title="Template talk:Organ system development"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Organ_system_development" title="Special:EditPage/Template:Organ system development"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Oxygenation,_nutrient,_and_waste_exchange"><span id="Oxygenation.2C_nutrient.2C_and_waste_exchange"></span>Oxygenation, nutrient, and waste exchange</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=1" title="Edit section: Oxygenation, nutrient, and waste exchange"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Placenta">Placenta</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=2" title="Edit section: Placenta"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The placenta functions as the exchange site of nutrients and wastes between the maternal and fetal circulation.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Water, glucose, amino acids, vitamins, and inorganic salts freely diffuse across the placenta along with oxygen. Two <a href="/wiki/Umbilical_arteries" class="mw-redirect" title="Umbilical arteries">umbilical arteries</a> carry systemic arterial blood from the fetus to the placenta where waste is exchanged for oxygen and nutrients. The oxygenated blood will then return to the fetus from the placenta via the <a href="/wiki/Umbilical_vein" title="Umbilical vein">umbilical vein</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Oxygenation_transport_in_fetus">Oxygenation transport in fetus</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=3" title="Edit section: Oxygenation transport in fetus"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hemoglobin is a structure found within the red blood cells that binds to and carries oxygen. <a href="/wiki/Fetal_hemoglobin" title="Fetal hemoglobin">Fetal hemoglobin</a> enhances the fetus' ability to draw oxygen from the placenta. This is facilitated by the hemoglobin molecule that made up of two <a href="/wiki/Hemoglobin,_alpha_1" class="mw-redirect" title="Hemoglobin, alpha 1">alpha</a> and two <a href="/wiki/HBG1" title="HBG1">gamma chains</a> (2α2γ). Its <a href="/wiki/Oxygen-hemoglobin_dissociation_curve" class="mw-redirect" title="Oxygen-hemoglobin dissociation curve">oxygen-hemoglobin dissociation curve</a> is shifted to the left, meaning that it is able to absorb oxygen at lower concentrations than adult hemoglobin. This enables fetal hemoglobin to absorb oxygen from adult hemoglobin in the placenta, where the oxygen pressure is lower than at the lungs. Around 6 months of age after birth, the gamma chains will gradually be replaced by <a href="/wiki/HBB" class="mw-redirect" title="HBB">beta chains</a>. This new hemoglobin structure is known as hemoglobin A, composed of two alpha and two beta chains (2α2β).<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Hemoglobin A is the predominant form found in adults. </p> <div class="mw-heading mw-heading2"><h2 id="Before_birth">Before birth</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=4" title="Edit section: Before birth"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Fetal_circulation.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Fetal_circulation.png/220px-Fetal_circulation.png" decoding="async" width="220" height="355" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Fetal_circulation.png/330px-Fetal_circulation.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Fetal_circulation.png/440px-Fetal_circulation.png 2x" data-file-width="558" data-file-height="900" /></a><figcaption>Diagram of the human fetal circulatory system.</figcaption></figure> <p>Oxygenated blood from the placenta is carried to the fetus by the umbilical vein, which will drain into the <a href="/wiki/Inferior_vena_cava" title="Inferior vena cava">inferior vena cava (IVC)</a> through the <a href="/wiki/Ductus_venosus" title="Ductus venosus">ductus venosus</a> or the liver.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> When oxygenated blood enters the IVC, it moves in parallel with deoxygenated blood from the fetal systemic veins, establishing a bilaminar blood flow as it enters the right atrium.<sup id="cite_ref-:1_2-1" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>The fetal heart contains two upper <a href="/wiki/Atrium_(heart)" title="Atrium (heart)">atria</a> and two lower <a href="/wiki/Ventricle_(heart)" title="Ventricle (heart)">ventricles</a>. It also contains two additional structures, the <a href="/wiki/Foramen_ovale_(heart)" title="Foramen ovale (heart)">foramen ovale</a> and the <a href="/wiki/Ductus_arteriosus" title="Ductus arteriosus">ductus arteriosus</a>, that function as shunts for oxygenated blood.<sup id="cite_ref-:1_2-2" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The function of these shunts is to bypass the <a href="/wiki/Lung" title="Lung">lungs</a> and maintain proper circulation to important fetal tissue. In the fetal stage, the lungs fill with fluid and collapse because the fetus is within the <a href="/wiki/Amniotic_sac" title="Amniotic sac">amniotic sac</a> and the placenta is providing the oxygen it needs to grow. With the lung collapsed, pulmonary <a href="/wiki/Vascular_resistance" title="Vascular resistance">vascular resistance</a> remains high during the fetal stage to prevent blood flow into the lungs.<sup id="cite_ref-:1_2-3" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> As oxygenated blood arrives at the right atrium, the <a href="/wiki/Eustachian_valve" class="mw-redirect" title="Eustachian valve">eustachian valve</a> helps direct the oxygenated blood into the foramen ovale, an opening between the right and left atrium. As the blood flows through the left atrium, it will move through the <a href="/wiki/Mitral_valve" title="Mitral valve">mitral valve</a> into the left ventricle and will be pumped through the aorta into the body. The shunting of oxygenated blood from right to left atrium will supply blood high in oxygen and nutrient content to the upper extremities, including the critically important brain. Some of the blood moves from the aorta through the <a href="/wiki/Internal_iliac_artery" title="Internal iliac artery">internal iliac arteries</a> to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation.<sup id="cite_ref-:0_1-1" class="reference"><a href="#cite_note-:0-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:1_2-4" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle. This blood consists of oxygenated placental blood and deoxygenated blood returning from the fetal circulation.<sup id="cite_ref-:1_2-5" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> This blood is pumped into the <a href="/wiki/Pulmonary_artery" title="Pulmonary artery">pulmonary artery</a>. At the pulmonary artery, it is met with high pulmonary vascular resistance as a result of collapsed lungs and pulmonary capillaries.  In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus.<sup id="cite_ref-:1_2-6" class="reference"><a href="#cite_note-:1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Because the <a href="/wiki/Aorta" title="Aorta">aorta</a> has lower pressure than the pulmonary artery, most of the blood flows across the ductus arteriosus away from the lungs.<sup id="cite_ref-:0_1-2" class="reference"><a href="#cite_note-:0-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Once the blood goes through the ductus arteriosus, it mixes with the blood from the aorta. This results in mixed blood oxygen saturation that supplies most of the structures of the lower half of the fetal body.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="After_birth">After birth</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=5" title="Edit section: After birth"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Adaptation_to_extrauterine_life" title="Adaptation to extrauterine life">Adaptation to extrauterine life</a></div> <p>As the umbilical vessels are obliterated and the infant starts breathing at birth, the source of oxygen changes from the placenta to the lungs. This major trigger will facilitate the transformation from fetal to postnatal circulation in many ways. </p><p>First, the ductus venosus was previously kept open by the blood flow from the umbilical vein. The reduced blood flow through the umbilical vein at birth will collapse and close the ductus venosus.  Hence, the IVC will only carry deoxygenated blood from the infant's organs and lower extremities. Second, as the infant breathes, the lungs will expand and fill the <a href="/wiki/Pulmonary_alveolus" title="Pulmonary alveolus">alveoli</a> with oxygen. The increased oxygen content will dilate the pulmonary capillaries and also trigger the release of <a href="/wiki/Nitric_oxide" title="Nitric oxide">nitric oxide</a>, which further dilates the blood vessels within the lungs. Together, these forces will decrease the pulmonary vascular resistance.<sup id="cite_ref-yg_7-0" class="reference"><a href="#cite_note-yg-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>With decreased resistance in the lungs, there will be increased blood flow to the lungs from the right ventricle of the heart through the pulmonary arteries, establishing the newborn's pulmonary circulation. With each of the newborn's breaths, blood perfuses the pulmonary capillary beds and undergoes oxygenation before exiting the lungs via the <a href="/wiki/Pulmonary_vein" title="Pulmonary vein">pulmonary veins</a> and returning to the heart. Thus, as more blood flows through the pulmonary circulation, there will be a higher volume of blood returning to the left atrium from the lungs. The increased venous return will elevate the pressure of the left atrium until it exceeds the pressure of the right atrium. The difference in pressure between these two chambers of the heart will close the foramen ovale. </p><p>Lastly, due to the decreased pulmonary vascular resistance, the pressure of the pulmonary artery will fall until it is lower than the pressure of the aorta. Since blood flows from high to low pressure systems, the direction of blood flow across the ductus arteriosus reverses. As the oxygen-rich blood from the aorta flows across the ductus arteriosus to the pulmonary artery, the ductus arteriosus will constrict in response to the high oxygen content of the blood. While oxygen serves as a vasoconstrictor of the ductus arteriosus, <a href="/wiki/Prostaglandin" title="Prostaglandin">prostaglandins</a> can keep the ductus arteriosus open to maintain blood flow to the lower extremities in cases of <a href="/wiki/Hypoplastic_left_heart_syndrome" title="Hypoplastic left heart syndrome">hypoplastic left heart syndrome</a> where the mitral valve is shut. The removal of the placenta, a source of prostaglandin, is another mechanism by which the ductus arteriosus closes at birth.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Within the next 2 to 3 weeks, the constriction results in decreased blood flow to the structure which induces the death of the tissue to keep the structure permanently closed.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>As a result of these changes, postnatal circulation will direct deoxygenated blood from the inferior and superior vena cava to the right heart, from which the blood will flow to the lungs via the pulmonary circulation. Blood will be oxygenated in the lungs and return to the left heart, which will pump oxygen-rich blood out through the aorta to supply the rest of the body via the systemic circulation. </p><p>In certain cases, the transition from fetal to postnatal circulation may not occur as described above due to complications leading to persistently high pulmonary vascular resistance. Preterm infants are born without fully mature lungs lacking the <a href="/wiki/Surfactant" title="Surfactant">surfactant</a> compound that allows alveoli to remain open by overcoming the surface tension of water.<sup id="cite_ref-:2_10-0" class="reference"><a href="#cite_note-:2-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> The resulting difficulty in lung expansion prevents the necessary reduction in pulmonary vascular resistance for the infant to make the normal cardiopulmonary transition, resulting in <a href="/wiki/Infant_respiratory_distress_syndrome" title="Infant respiratory distress syndrome">infant respiratory distress syndrome</a>.<sup id="cite_ref-:2_10-1" class="reference"><a href="#cite_note-:2-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> In addition, occasionally during birth, infants may inhale remnants of their fecal matter known as <a href="/wiki/Meconium" title="Meconium">meconium</a>, preventing adequate breathing.<sup id="cite_ref-:3_11-0" class="reference"><a href="#cite_note-:3-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The presence of meconium within the lungs, known as <a href="/wiki/Meconium_aspiration_syndrome" title="Meconium aspiration syndrome">meconium aspiration syndrome</a>, can obstruct the airways and also deactivate the newborn's surfactant. The inflammation that also results from the inhalation of meconium also causes airway constriction, resulting in poor ventilation of the alveoli and inadequate oxygenation of the pulmonary capillary beds.<sup id="cite_ref-:3_11-1" class="reference"><a href="#cite_note-:3-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> With a lack of oxygen entering the lungs, pulmonary vascular resistance will remain high and the newborn's blood will no longer be oxygenated, preventing fetal shunt closure. </p><p>In both cases of infant respiratory distress syndrome and meconium aspiration syndrome, fetal shunts will remain open due to the high pulmonary vascular resistance until appropriate measures, such as administration of surfactant or mechanical ventilation, are taken to help the infant breathe on its own. If the problem is not corrected, the infant will undergo hypoxia, acidosis, and other serious complications, such as seizures. </p> <div class="mw-heading mw-heading2"><h2 id="Adult_remnants">Adult remnants</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=6" title="Edit section: Adult remnants"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Remnants of the fetal circulation can be found in the adult.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable" style="line-height:1.3em"> <tbody><tr> <th>Fetal </th> <th>Develops </th></tr> <tr> <td><i><a href="/wiki/Foramen_ovale_(heart)" title="Foramen ovale (heart)">foramen ovale</a></i> </td> <td><i><a href="/wiki/Fossa_ovalis_(heart)" title="Fossa ovalis (heart)">fossa ovalis</a></i> </td></tr> <tr> <td><i><a href="/wiki/Ductus_arteriosus" title="Ductus arteriosus">ductus arteriosus</a></i> </td> <td><i><a href="/wiki/Ligamentum_arteriosum" title="Ligamentum arteriosum">ligamentum arteriosum</a></i> </td></tr> <tr> <td>extra-<a href="/wiki/Hepatic" class="mw-redirect" title="Hepatic">hepatic</a> portion of the fetal left <a href="/wiki/Umbilical_vein" title="Umbilical vein">umbilical vein</a> </td> <td><i><a href="/wiki/Ligamentum_teres_hepatis" class="mw-redirect" title="Ligamentum teres hepatis">ligamentum teres hepatis</a></i><br />("round ligament of the liver") </td></tr> <tr> <td>intra-hepatic portion of the fetal left umbilical vein<br />(<i><a href="/wiki/Ductus_venosus" title="Ductus venosus">ductus venosus</a></i>) </td> <td><i><a href="/wiki/Ligamentum_venosum" title="Ligamentum venosum">ligamentum venosum</a></i> </td></tr> <tr> <td><a href="/wiki/Anatomical_terms_of_location#Proximal_and_distal" title="Anatomical terms of location">proximal</a> portions of the fetal left and right <a href="/wiki/Umbilical_artery" title="Umbilical artery">umbilical arteries</a>  </td> <td><a href="/wiki/Umbilical_branches" class="mw-redirect" title="Umbilical branches">umbilical branches</a> of the <a href="/wiki/Internal_iliac_arteries" class="mw-redirect" title="Internal iliac arteries">internal iliac arteries</a>  </td></tr> <tr> <td><a href="/wiki/Anatomical_terms_of_location#Proximal_and_distal" title="Anatomical terms of location">distal</a> portions of the fetal left and right umbilical arteries </td> <td><a href="/wiki/Lateral_umbilical_ligament" class="mw-redirect" title="Lateral umbilical ligament">umbilical ligaments</a> </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Physiology">Physiology</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=7" title="Edit section: Physiology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The core concept behind fetal circulation is that <a href="/wiki/Fetal_hemoglobin" title="Fetal hemoglobin">fetal hemoglobin</a> (HbF)<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> has a higher affinity for oxygen than does adult <a href="/wiki/Hemoglobin" title="Hemoglobin">hemoglobin</a>, which, together with the difference in partial pressure of oxygen, allows a diffusion of oxygen from the mother's circulatory system to the fetus. </p> <div class="mw-heading mw-heading3"><h3 id="Blood_pressure">Blood pressure</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=8" title="Edit section: Blood pressure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>It is the fetal heart and not the mother's heart that builds up the fetal blood pressure to drive its blood through the fetal circulation. </p><p>Intracardiac pressure remains identical between the right and left ventricles of the human fetus.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p><p>The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation, and increases to ca 45 mmHg at 40 weeks of gestation.<sup id="cite_ref-Struijk_16-0" class="reference"><a href="#cite_note-Struijk-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The fetal <a href="/wiki/Pulse_pressure" title="Pulse pressure">pulse pressure</a> is ca 20 mmHg at 20 weeks of gestation, increasing to ca 30 mmHg at 40 weeks of gestation.<sup id="cite_ref-Struijk_16-1" class="reference"><a href="#cite_note-Struijk-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p>The blood pressure decreases when passing through the placenta. In the <a href="/wiki/Arteria_umbilicalis" class="mw-redirect" title="Arteria umbilicalis">arteria umbilicalis</a>, it is ca 50 mmHg. It falls to 30 mmHg in the capillaries in the villi. Subsequently, the pressure is 20 mm Hg in the umbilical vein, returning to the heart.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Flow">Flow</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=9" title="Edit section: Flow"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The blood flow through the umbilical cord is approximately 35 mL/min at 20 weeks, and 240 mL/min at 40 <a href="/wiki/Gestational_age_(obstetrics)" class="mw-redirect" title="Gestational age (obstetrics)">weeks of gestation</a>.<sup id="cite_ref-kiserud2004_18-0" class="reference"><a href="#cite_note-kiserud2004-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> Adapted to the weight of the fetus, this corresponds to 115 mL/min/kg at 20 weeks and 64 mL/min/kg at 40 weeks.<sup id="cite_ref-kiserud2004_18-1" class="reference"><a href="#cite_note-kiserud2004-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> It corresponds to 17% of the <a href="/wiki/Combined_cardiac_output" class="mw-redirect" title="Combined cardiac output">combined cardiac output</a> of the fetus at 10 weeks, and 33% at 20 weeks of gestation.<sup id="cite_ref-kiserud2004_18-2" class="reference"><a href="#cite_note-kiserud2004-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Endothelin" title="Endothelin">Endothelin</a> and <a href="/wiki/Prostanoid" title="Prostanoid">prostanoids</a> cause <a href="/wiki/Vasoconstriction" title="Vasoconstriction">vasoconstriction</a> in placental arteries, while <a href="/wiki/Nitric_oxide" title="Nitric oxide">nitric oxide</a> causes <a href="/wiki/Vasodilation" title="Vasodilation">vasodilation</a>.<sup id="cite_ref-kiserud2004_18-3" class="reference"><a href="#cite_note-kiserud2004-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> On the other hand, there is no neural vascular regulation, and catecholamines have only little effect.<sup id="cite_ref-kiserud2004_18-4" class="reference"><a href="#cite_note-kiserud2004-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Additional_images">Additional images</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=10" title="Edit section: Additional images"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul class="gallery mw-gallery-traditional"> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Neonatal_Heart_Circulation.png" class="mw-file-description" title="Neonatal heart circulation"><img alt="Neonatal heart circulation" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Neonatal_Heart_Circulation.png/120px-Neonatal_Heart_Circulation.png" decoding="async" width="120" height="71" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Neonatal_Heart_Circulation.png/180px-Neonatal_Heart_Circulation.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/76/Neonatal_Heart_Circulation.png/240px-Neonatal_Heart_Circulation.png 2x" data-file-width="1100" data-file-height="650" /></a></span></div> <div class="gallerytext">Neonatal heart circulation</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:8w3d_with_umbilical_cord.gif" class="mw-file-description" title="Obstetric ultrasonography of an embryo of 8 weeks with visible heartbeat."><img alt="Obstetric ultrasonography of an embryo of 8 weeks with visible heartbeat." src="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/8w3d_with_umbilical_cord.gif/115px-8w3d_with_umbilical_cord.gif" decoding="async" width="115" height="120" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/8w3d_with_umbilical_cord.gif/173px-8w3d_with_umbilical_cord.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/4/41/8w3d_with_umbilical_cord.gif 2x" data-file-width="227" data-file-height="236" /></a></span></div> <div class="gallerytext"><a href="/wiki/Obstetric_ultrasonography" title="Obstetric ultrasonography">Obstetric ultrasonography</a> of an embryo of 8 weeks with visible heartbeat.</div> </li> </ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fetal_circulation&action=edit&section=11" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 35em;"> <ol class="references"> <li id="cite_note-:0-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_1-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration 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.cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.r2library.com/resource/title/1439059438">"Comprehensive Perinatal & Pediatric Respiratory Care | R2 Digital Library"</a>. <i>www.r2library.com</i><span class="reference-accessdate">. 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title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Prenatal+Diagnosis&rft.atitle=The+fetal+circulation&rft.volume=24&rft.issue=13&rft.pages=1049-59&rft.date=2004&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A25040285%23id-name%3DS2CID&rft_id=info%3Apmid%2F15614842&rft_id=info%3Adoi%2F10.1002%2Fpd.1062&rft.aulast=Kiserud&rft.aufirst=Torvid&rft.au=Acharya%2C+Ganesh&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFetal+circulation" class="Z3988"></span></span> </li> </ol></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output 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.navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Development_of_the_circulatory_system" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Development_of_mammalian_circulatory_system" title="Template:Development of mammalian circulatory system"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Development_of_mammalian_circulatory_system" title="Template talk:Development of mammalian circulatory system"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Development_of_mammalian_circulatory_system" title="Special:EditPage/Template:Development of mammalian circulatory system"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Development_of_the_circulatory_system" style="font-size:114%;margin:0 4em">Development of the <a href="/wiki/Circulatory_system" title="Circulatory system">circulatory system</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Heart_development" title="Heart development">Heart</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Tubular_heart" title="Tubular heart">Tubular heart</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Truncus_arteriosus" title="Truncus arteriosus">Truncus arteriosus</a></li> <li><a href="/wiki/Bulbus_cordis" title="Bulbus cordis">Bulbus cordis</a></li> <li><a href="/wiki/Primitive_ventricle" title="Primitive ventricle">Primitive ventricle</a></li> <li><a href="/wiki/Primitive_atrium" title="Primitive atrium">Primitive atrium</a></li> <li><a href="/wiki/Sinus_venosus" title="Sinus venosus">Sinus venosus</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Chamber formation</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Atrioventricular <ul><li><a href="/wiki/Primary_interventricular_foramen" title="Primary interventricular foramen">Primary interventricular foramen</a></li> <li><a href="/wiki/Endocardial_cushions" title="Endocardial cushions">Endocardial cushions</a></li> <li><a href="/wiki/Septum_intermedium" title="Septum intermedium">Septum intermedium</a></li> <li><a href="/wiki/Atrioventricular_canal" title="Atrioventricular canal">Atrioventricular canal</a></li></ul></li> <li>Atrial <ul><li><a href="/wiki/Septum_primum" title="Septum primum">Septum primum</a></li> <li><a href="/wiki/Foramen_secundum" title="Foramen secundum">Foramen secundum</a></li> <li><a href="/wiki/Primary_interatrial_foramen" title="Primary interatrial foramen">Primary interatrial foramen</a></li> <li><a href="/wiki/Septum_secundum" title="Septum secundum">Septum secundum</a></li> <li><a href="/wiki/Foramen_ovale_(heart)" title="Foramen ovale (heart)">Foramen ovale</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aorticopulmonary_septum" title="Aorticopulmonary septum">Aorticopulmonary septum</a></li> <li><a href="/wiki/Protein_signalling_in_heart_development" title="Protein signalling in heart development">Protein signalling in heart development</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Vessels</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Angiogenesis" title="Angiogenesis">Arteries</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Dorsal_aorta" title="Dorsal aorta">Dorsal aorta</a></li> <li><a href="/wiki/Aortic_arches" title="Aortic arches">Aortic arches</a></li> <li><a href="/wiki/Aortic_sac" title="Aortic sac">Aortic sac</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vasculogenesis" title="Vasculogenesis">Veins</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Anterior_cardinal_vein" title="Anterior cardinal vein">Anterior cardinal vein</a></li> <li><a href="/wiki/Posterior_cardinal_vein" title="Posterior cardinal vein">Posterior cardinal vein</a></li> <li><a href="/wiki/Common_cardinal_veins" title="Common cardinal veins">Common cardinal veins</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Lymphangiogenesis" title="Lymphangiogenesis">Lymph vessels</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lymph_sacs" title="Lymph sacs">Lymph sacs</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Vascular_remodelling_in_the_embryo" title="Vascular remodelling in the embryo">Vascular remodelling in the embryo</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Extraembryonic<br /><a href="/wiki/Haematopoiesis#Locations" title="Haematopoiesis">hemangiogenesis</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Blood_islands" title="Blood islands">Blood islands</a></li> <li><a href="/wiki/Chorion" title="Chorion">Chorion</a></li> <li><a href="/wiki/Connecting_stalk" title="Connecting stalk">Connecting stalk</a></li> <li><a href="/wiki/Yolk_sac" title="Yolk sac">Yolk sac</a></li> <li><a href="/wiki/Placenta" title="Placenta">Placenta</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a class="mw-selflink selflink">Fetal circulation</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Umbilical_cord" title="Umbilical cord">umbilical cord</a>: <a href="/wiki/Umbilical_vein" title="Umbilical vein">Umbilical vein</a> → <a href="/wiki/Ductus_venosus" title="Ductus venosus">Ductus venosus</a> → <a href="/wiki/Inferior_vena_cava" title="Inferior vena cava">Inferior vena cava</a> → <a href="/wiki/Heart" title="Heart">Heart</a> → <a href="/wiki/Pulmonary_artery" title="Pulmonary artery">Pulmonary artery</a> → <a href="/wiki/Ductus_arteriosus" title="Ductus arteriosus">Ductus arteriosus</a> → <a href="/wiki/Aorta" title="Aorta">Aorta</a> → <a href="/wiki/Umbilical_artery" title="Umbilical artery">Umbilical artery</a></li></ul> <ul><li><a href="/wiki/Yolk_sac" title="Yolk sac">yolk sac</a>: <a href="/wiki/Vitelline_veins" title="Vitelline veins">Vitelline veins</a></li> <li><a href="/wiki/Vitelline_arteries" title="Vitelline arteries">Vitelline arteries</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Fetal_circulation&oldid=1258833490">https://en.wikipedia.org/w/index.php?title=Fetal_circulation&oldid=1258833490</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Category</a>: <ul><li><a href="/wiki/Category:Embryology_of_cardiovascular_system" title="Category:Embryology of cardiovascular system">Embryology of cardiovascular system</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a 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