Why should you not cut the umbilical cord right away?

Cutting the cord too soon after birth might stress the baby’s heart, increase the risk for bleeding inside the brain, and increase the risk for anemia and iron deficiency. Waiting too long may result in the infant having too many red blood cells. The excess red cells could lead to newborn jaundice, a kind of blood poisoning resulting from the breakdown of the extra red cells.

From the National Institutes of Health, I’m Barrett Whitener, and this is “Research Developments,” a podcast from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NICHD.

Recently, Australian scientist Stuart Hooper reviewed the major studies on the science of when to clamp the umbilical cord after birth. Much of this extensive body of research was funded by the NICHD. To help us understand these findings, we have invited Dr. Tonse Raju, Chief of NICHD’s Pregnancy and Perinatology Branch.

Before we get started, let’s stop to consider for a minute the incredible transition an infant’s heart and lungs must make shortly after birth. In the womb, the lungs cannot take in air, so the baby doesn’t inhale and exhale. The lungs are filled with fluid. Adults get oxygen from the lungs, but the fetus gets its oxygen from the umbilical cord. The two chambers of the infant heart beat at roughly the same interval, to bring oxygen from the umbilical region to the tissues and send it back again. At birth, this arrangement changes rapidly. The blood flow switches, so that now it fills the lungs.

Now, here’s the reason for concern: If you cut the cord before the infant clears its lungs, takes that first breath, and transitions its blood circulation to the lungs, you could deprive it of blood and oxygen—and also stress the heart.