Minutes after a baby girl was born on a recent morning at the University of California hospital in San Francisco, her placenta — a pulpy blob of an organ that is usually thrown away — was packed up and carried off like treasure through a maze of corridors to the laboratory of Susan Fisher, a professor of obstetrics, gynaecology and reproductive sciences.
There, scientists set upon the tissue with scalpels, forceps and an array of chemicals to extract its weirdly powerful cells, which storm the uterus like an invading army and commandeer a woman’s body for nine months to keep her foetus alive. The placenta is the life support system for the foetus. A disk of tissue attached to the uterine lining on one side and to the umbilical cord on the other, it grows from the embryo’s cells, not the mother’s. It is sometimes called the afterbirth: It comes out after the baby is born, usually weighing about a pound, or a sixth of the baby’s weight.
It provides oxygen, nourishment and waste disposal, doing the job of the lungs, liver, kidneys and other organs until the foetal ones kick in. If something goes wrong with the placenta, devastating problems can result, including miscarriage, stillbirth, prematurity, low birth weight and pre-eclampsia, a condition that drives up the mother’s blood pressure and can kill her and the foetus. Increasingly, researchers think placental disorders can permanently alter the health of mother and child.
Given its vital role, shockingly little is known about the placenta. Only recently, for instance, did scientists start to suspect that the placenta may not be sterile, as once thought, but may have a microbiome of its own — a population of micro-organisms — that may help shape the immune system of the foetus and affect its health much later in life.
Fisher and other researchers have studied the placenta for decades, but she said: “Compared to what we should know, we know almost nothing. It’s a place where I think we could make real medical breakthroughs.”
The National Institute of Child Health and Human Development calls the placenta “the least understood human organ and arguably one of the more important, not only for the health of a woman and her foetus during pregnancy but also for the lifelong health of both.”
In May, the institute gathered about 70 scientists at its first conference devoted to the placenta, in hopes of starting a Human