Question

Which hormone is responsible for stimulating uterine muscle growth throughout pregnancy?

A. Throughout pregnancy, rising concentrations of estrogen stimulate uterine muscle growth
B. Estrogen levels are low throughout the first 4 months of pregnancy, but increase rapidly thereafter
C. Throughout pregnancy, rising concentrations of progesterone promote uterine contractility

Answer 1

Estrogen is the hormone responsible for stimulating uterine muscle growth throughout pregnancy. The role of progesterone is to inhibit contractions early on, but its levels decrease later in pregnancy, allowing estrogen to dominate and prepare the uterus for labor.

Step-by-step explanation:

The hormone responsible for stimulating uterine muscle growth throughout pregnancy is estrogen. During the first several months of pregnancy, progesterone plays a key role in inhibiting uterine contractions to protect the developing fetus. However, as the pregnancy progresses into the seventh month, progesterone levels plateau and eventually decrease, while estrogen levels continue to rise. This rise in estrogen makes the myometrium, which is the uterine smooth muscle, more sensitive to stimuli and promotes contractions once progesterone's inhibitory effect wanes. Moreover, the surge in fetal cortisol during the eighth month boosts estrogen secretion by the placenta, further influencing uterine muscle growth and preparing the body for labor.