ABSTRACT
Prostaglandins play a key role in human labor in that prostaglandins can cause abortion
or labor and prostaglandin antagonists can inhibit preterm labor. However, the factors
determining prostaglandin synthesis and release in human pregnancy are uncertain.
An increase in the synthesis of prostaglandins at the start of labor could result
from either increased release of free arachidonic acid or removal of constraint on
prostaglandin H synthase activity, or both. The points in the biosynthetic pathway
of prostaglandins at which control could be exerted physiologically are examined,
with emphasis on the phospholipases.
