Which is the most likely cause of these findings? A healthy 26-year-old woman delivers a single chorion and placenta but two amniotic sacs following a normal, full-term delivery.

Monozygotic twins

The correct answer is D. This woman has had a normal delivery of monozygotic (identical) twins. Monozygotes may also develop separately, producing two amniotic sacs, two placentas, and two chorions, but this would not be distinguishable from dizygotic twins. In the case of a single chorion and placenta, the pregnancy must have developed from a single zygote, and in the womb the identical twins would appear within a single chorion with separate amniotic sacs Answer A is incorrect. Chorioamnionitis is typically caused by an infection ascending from the cervix or vagina following a premature membrane rupture. It requires early delivery and has a high risk of mortality for the fetus and would not, therefore, be considered a normal delivery Answer B is incorrect. A complete hydatidiform mole would not produce a normal delivery. Gross pathology shows a single enlarged placenta with edematous villi resembling grapes. Clinically, it produces a significant increase in human chorionic gonadotropin, vaginal bleeding, and fast uterine growth. It confers a 2%3% risk of choriocarcinoma. Complete moles have no embryo present and are exclusively of paternal derivation Answer C is incorrect. Dizygotic twins would produce two chorions and two placentas, as well as two amniotic sacs Answer E is incorrect. Sheehans syndrome is postpartum anterior pituitary necrosis resulting from hypotension and infarction following blood loss in pregnancy. It causes the gradual loss of anterior pituitary function. It has no relation to multiple amniotic sacs.