Prostacyclin synthesis stimulating plasma factor in pregnancy and puerperium.

Prostacyclin is assumed to play a key role in maintaining a sufficient blood flow in maternal and fetal circulation. Recent reports pointed out that the prostacyclin synthesis is regulated by a so-called plasma factor. The activity of this plasma factor was tested during pregnancy, labor, and puerperium. During the first and second trimesters, increased values could be observed, whereas in the third trimester and at the onset of labor, the values decreased. After delivery, there was again a moderate increase in plasma factor activity. A feedback mechanism is discussed between prostacyclin or 6-oxo-prostaglandin F1 alpha and the plasma factor, but hormones, such as 17 beta-estradiol, may possibly influence prostacyclin synthesis in pregnancy.