Peristalsis and uterine contractility would increase.

This is because progesterone is a hormone that relaxes the smooth muscles of the uterus and the gastrointestinal tract during pregnancy.

If progesterone were reduced or withdrawn, the uterus would contract more and peristalsis would increase, leading to possible preterm labor and digestive problems.

Choice A is wrong because insulin resistance would be decreased, not increased, by lower progesterone levels.

Progesterone increases insulin resistance during pregnancy to ensure adequate glucose supply for the fetus.

Choice B is wrong because sweat and sebaceous glands would decrease production, not increase, by lower progesterone levels.

Progesterone stimulates the activity of these glands during pregnancy to regulate body temperature and protect the skin from infections.

Choice C is wrong because pyrosis (heartburn) would decrease in frequency, not increase, by lower progesterone levels.

Progesterone relaxes the lower esophageal sphincter during pregnancy, allowing gastric acid to reflux into the esophagus and cause pyrosis.