Medication-prenatal

Medication-prenatal

We are all too aware of the fetus’s vulnerability, in which the placenta seems not an unbreachable barrier but the merest wisp. What is the placenta capable of blocking, I wonder, and what does it allow to pass through? To find out, I call Gideon Koren, professor of pediatrics and pharmacology at the University of Toronto and director of the Motherisk program at Toronto’s Hospital for Sick Children. Motherisk runs the busiest hotline in the world for pregnant women with questions about exposures to drugs, chemicals, and diseases; its operators field hundreds of calls a week.

“During most of pregnancy, the placenta separating mother and fetus is only one cell thick,” Koren tells me. “But it has an array of mechanisms to help it do its job of protecting the fetus.” These subcellular tools, he explains, include tiny pumps that expel toxins before they can do any damage, immune agents that guard the placenta’s perimeter, and placental enzymes that chemically break down intruding molecules.

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