Pregnancy Battle Between Uterus and Placenta

Conflicting jobs may explain preeclampsia

/ Author:  / Reviewed by: Joseph V. Madia, MD

The womb during pregnancy is somewhat of a battleground. The mother's uterus carries the fetus, and must keep it small enough to pass through the birth canal. This is in conflict with the placenta, made up of cells contributed by the father, that has a biological goal of producing the biggest, healthiest baby possible.

Therein lies the struggle: the baby must grow and thrive, yet be able to be born without complications to the mother. These conflicting mechanisms might help explain preeclampsia, an often deadly condition of pregnancy that results in high blood pressure and protein in the mother's urine. The only known cure for preeclampsia is to deliver the baby.

A study at the Yale School of Medicine looked at the way the placenta and uterus interact during pregnancy. The placenta is made up of cells called trophoblasts (controlled by the father), which increase the flow of the mother's blood into the placenta. The placenta's job is to get the most nutrients possible to the fetus, and to do so it basically tricks the mother into not attacking these foreign cells. If the deception doesn't work, the mother may develop preeclampsia.

Harvey J. Kliman, M.D., research scientist in the Department of Obstetrics, Gynecology & Reproductive Sciences at Yale, led a team of researchers in observing this phenomenon. As the placental trophoblast cells invade, the mother's own lymphocyte cells go on alert, with a natural reaction to destroy the invasive cells.

The placenta then creates a sort of diversion, by secreting a protein to occupy the lymphocyte cells, so that the trophoblasts can do their work and the baby grows.

The process appears to be an extremely delicate balancing act. The entire area around these veins becomes a mass of inflammation and dead cells, called necrosis.

“We realized that these zones of necrosis are likely occupying the mother’s soldiers while the invasive trophoblasts sneak into her arteries, leading to more blood flow to the placenta and a bigger baby,” said Kliman. “We believe that maintaining this balance could be the key to a healthy pregnancy free from preeclampsia.”

The findings are published in the online issue of Reproductive Sciences.

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Review Date: 
October 13, 2011