MICROANATOMY

Detailed explanation-1: -Like estrogen, progesterone suppresses FSH and LH. It also inhibits uterine contractions, protecting the fetus from preterm birth. This hormone decreases in late gestation, allowing uterine contractions to intensify and eventually progress to true labor. The placenta also produces hCG.

Detailed explanation-2: -Estrogen increases oxytocin receptor expression and progesterone suppresses such estrogen-induced increase in cultured human myometrial cells. [69] Oxytocin induces uterine contractions in two ways. Oxytocin stimulates the release of PGE2 and prostaglandin F2 in fetal membranes by activation of phospholipase C.

Detailed explanation-3: -Thus, the process of parturition and in particular the transformation of the myometrium from a quiescent to a contractile state, requires progesterone withdrawal and estrogen activation, which in most mammals are achieved by changes in circulating progesterone (decrease) and estrogen (increase) levels (2, 3).