Final answer:
Progesterone is known as the 'hormone of pregnancy' due to its role in reducing uterine contractions to prevent preterm labor. Its levels drop in later stages of pregnancy, enabling labor contractions to begin. Oxytocin then takes over to stimulate labor contractions necessary for childbirth.
Step-by-step explanation:
The hormone that is often referred to as the “hormone of pregnancy” because it reduces uterine contractions during pregnancy is progesterone. This hormone is crucial for maintaining the uterine lining and keeping the uterus calm during the early stages of pregnancy to prevent preterm labor. Progesterone levels remain high during the initial months but begin to drop as the pregnancy progresses, specifically after the seventh month. Consequently, the myometrium becomes more sensitive to contraction stimuli due to the decreasing progesterone and rising estrogen levels. However, it is noteworthy that towards the end of pregnancy, the hormone oxytocin increases in concentration, stimulating contractions necessary for childbirth. Oxytocin receptor expression and the uterus's sensitivity to this hormone also increase, setting the stage for labor
During the course of pregnancy, the placenta takes over progesterone synthesis, ensuring the hormone remains at levels necessary to suppress premature uterine contractions. As estrogen levels rise and the fetus matures, the hormone balance shifts, preparing the body for labor. While oxytocin plays an active role in inducing labor contractions, progesterone provides the opposite effect, demonstrating the intricate hormonal balance that underlies pregnancy and birth