Question

Which hormone is primarily responsible for the contractions during labor? a. oxytocin b. estrogen c. β-HCG d. progesterone

Short answer

The correct option is a. oxytocin .

Step-by-step solution

Step 1. Given ifnormation 

Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin.

Step 2. Explanation

The correct option is a. oxytocin .

Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin. At this time, the baby reorients, facing forward and down with the back or crown of the head engaging the cervix (uterine opening). This causes the cervix to stretch and nerve impulses are sent to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary