A new analysis upends traditional theories of why the placenta sometimes does not separate from the uterus at birth, a life-threatening complication that affects four million deliveries each year in the United States alone.
Typically, the placenta detaches from the uterine wall after childbirth and is delivered shortly after the baby emerges. In placenta accreta, the placenta grows too deeply into the wall of the uterus and part or all of it remains attached, resulting in hemorrhage and often in emergency hysterectomy.
It was previously thought that in cases of placenta accreta, placental cells called trophoblasts invade the uterus and keep the connection intact. The new study revealed important genetic and cellular changes inside the decidua – the layer of the uterine lining that forms during pregnancy to embrace and protect the embyro.
In cases of placenta accreta, normal boundary limits between the cells of the uterine lining and the growing placental blood vessels are lost, and the placenta ends up being attached too tightly, the researchers said.
For the new study, published on Monday in the American Journal of Obstetrics & Gynecology, researchers analyzed more than 31,000 individual cells obtained from 12 placentas – six with placenta accreta and six without. They also measured and mapped gene activity in tissue samples from the placentas.
“Our goal was to characterize the intimate relationship between the maternal and fetal tissue at the site of accreta or malfunction,” study leader Dr. Yalda Afshar of the David Geffen School of Medicine at UCLA said in a statement.
“The genes and signaling pathways we identified go beyond providing a better understanding of the mechanism of the disease; they may be used as targets to help us refine diagnostic tests, track disease progression over time, and discover new, more effective therapies.”
This newsletter was edited by Bill Berkrot.