The heart is one of the most important organs that help keep the systems in our body functioning. The four chambers and valves that make up our heart work together to provide a continuous blood flow and blood supply to our organs. The heart and circulatory system form soon after conception, and just like an adult heart, the prenatal heart develops the chambers and valves to pump blood throughout the body.
But the heart of a fetus is slightly different compared to that of a baby and an adult. The fetus does not use its own lungs until birth and gets oxygen solely from the mother’s placenta. The heart of a fetus does not need to pump blood to its lungs, so the circulatory system is different from that of a newborn baby.
The lungs of a fetus are essentially collapsed and are filled with fluid. There are two main structures that develop in the prenatal heart which allows blood to be routed around the lungs: the foramen ovale and the ductus arteriosus. The foramen ovale is an opening between the upper chambers, the left and right atria of the heart. The ductus arteriosus is a blood vessel which connects the aorta to the pulmonary artery. These two structures are part of the fetal circulatory system but disappear soon after birth.
In most babies, these two structures naturally close when the baby’s lungs inflate with air from their first breath and the cardiovascular system takes over. These changes are essential for the development of the human heart and is what allows us to maintain a strong and healthy lifestyle.
Remien K, Majmundar SH. (2021) Physiology, Fetal Circulation. Treasure Island (FL): StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539710/