PlacentaWhere the baby’s blood picks up oxygen and food from the mother.
Umbilical veinIt carries oxygen-rich blood from the placenta to the baby.
Ductus venosusA shortcut past the liver, straight to the inferior vena cava.
Foramen ovaleBlood passes through it, right atrium to left.
Ductus arteriosusIt carries blood from the pulmonary trunk into the aorta.
Internal iliac arteriesThe umbilical arteries branch from them, one on each side.
Umbilical arteriesTwo arteries that carry blood from the baby back to the placenta.
After birth: what is left 6
Fossa ovalisWhat is left of the foramen ovale after it closes.
Ligamentum arteriosumWhat is left of the ductus arteriosus after it closes.
Ligamentum venosumWhat is left of the ductus venosus after it closes.
Round ligament of the liverWhat is left of the umbilical vein; also called ligamentum teres.
Medial umbilical ligamentsWhat is left of the two umbilical arteries.
UmbilicusThe navel: the scar left where the umbilical cord was attached.
How this list was compiled: Every name and detail line was checked on 2026-09-30 against the US National Cancer Institute SEER Training Modules, Circulatory Pathways, https://training.seer.cancer.gov/anatomy/cardiovascular/blood/pathways.html; Kenhub, Fetal circulation, https://www.kenhub.com/en/library/anatomy/fetal-circulation, and Medial umbilical ligament, https://www.kenhub.com/en/library/anatomy/medial-umbilical-ligament; TeachMeAnatomy, The Liver, https://teachmeanatomy.info/abdomen/viscera/liver/; Wikipedia, Fetal circulation, text only; and Henry Gray, Anatomy of the Human Body, 1918 (public domain), https://archive.org/details/anatomyofhumanbo00grayrich. Hints and detail lines are in our own words. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work
How it works
This fetal heart diagram is a plan of the circulation before birth: the placenta, the cord’s vessels and the three shortcuts that carry blood past the liver and the lungs. A second view shows what each becomes after birth.
Read the full guide
Before birth
Before birth a baby gets oxygen from the placenta, not the lungs. The umbilical vein brings that blood in, and the ductus venosus lets it bypass the liver. In the heart the foramen ovale lets it cross from the right atrium to the left, and the ductus arteriosus joins the pulmonary trunk to the aorta. Two umbilical arteries, branches of the internal iliac arteries, take blood back to the placenta.
After birth
Switch to After birth to label what is left once those passages close: the fossa ovalis, the ligamentum arteriosum, the ligamentum venosum, the round ligament of the liver, the medial umbilical ligaments and the umbilicus.
The front of the body is on the left of the plan, so the navel and the cord are on that side.
The arrows show which way the blood flows.
Questions and answers
What are the three shunts in fetal circulation?
The ductus venosus, which lets blood from the umbilical vein bypass the liver; the foramen ovale, an opening that joins the two atria; and the ductus arteriosus, which joins the pulmonary trunk to the aorta. The last two let blood bypass the lungs.
Why does blood bypass the lungs before birth?
The lungs are not yet used for breathing. Oxygen comes from the mother’s blood at the placenta, so two shortcuts, the foramen ovale and the ductus arteriosus, let blood bypass them.
What do the fetal shunts become after birth?
The foramen ovale becomes the fossa ovalis, the ductus arteriosus the ligamentum arteriosum and the ductus venosus the ligamentum venosum. The umbilical vein becomes the round ligament of the liver, and the closed parts of the umbilical arteries the medial umbilical ligaments.
How many vessels are in the umbilical cord?
Three: one umbilical vein, which carries oxygen-rich blood from the placenta to the baby, and two umbilical arteries, which carry blood from the baby back to the placenta.