Final answer:
Afterpains are generally caused by hormonal changes, specifically the drop in progesterone and increased production of oxytocin, which lead to uterine contractions during labor and not by fetal distress.
Step-by-step explanation:
Afterpains, or intermittent uterine contractions, often occur due to hormonal changes, particularly the drop in progesterone levels towards the late stages of pregnancy. These contractions are a natural part of the labor process, serving to dilate the cervix and help expel the newborn. The contractions become more powerful as labor progresses due to a positive feedback loop involving cervical stretching, which triggers the release of oxytocin and results in more forceful contractions. Fetal distress can be a result of contractions that severely limit oxygenated blood flow to the fetus, not necessarily a cause of afterpains. Rather, afterpains are a result of the body's natural labor process, which includes the drop in progesterone, stretching of the uterus by the fetus, and the production of oxytocin leading to cervical dilation and the expulsion of the newborn.