theories

Question 1

As pregnancy nears, oxytocin production by the posterior pituitary gland increases while oxytocinase production by the placenta decreases, making the uterus more sensitive to oxytocin, which stimulates uterine contraction.

Answer 1

Oxytocin Stimulation Theory

Question 2

Any hollow muscular organ, when stretched to capacity, will contract and empty. As pregnancy advances, the distention of the uterus creates pressure on nerve endings, stimulating uterine contraction.

Answer 2

Uterine Stretch Theory

Question 3

Progesterone maintains pregnancy by relaxing the smooth muscles of the uterus. As pregnancy nears term, progesterone production decreases, leading to uterine contractions.

Answer 3

Progesterone Deprivation Theory

Question 4

When pregnancy reaches term, fetal membranes produce large amounts of arachidonic acid, which is converted by maternal deciduas into prostaglandin, initiating uterine contractions during labor.

Answer 4

Prostaglandin Theory

Question 5

As the placenta ages, it becomes less efficient, producing less progesterone and allowing concentrations of prostaglandin and estrogen to rise, resulting in rhythmic, regular, and strong uterine contractions.

Answer 5

Theory of the Aging Placenta

Question 6

This theory, proposed by Hippocrates, states that certain hormones produced by the fetal adrenal and pituitary glands initiate labor contractions.

Answer 6

Fetal Adrenal Response Theory