Case Study:

A 19-year-old woman is G2 P1. Her previous gestation resulted in a normal term birth at home. Her current pregnancy results in the birth of a 2990 gm baby at 35 weeks. At birth the infant appears hydropic and icteric, but no congenital anomalies are present. The baby's hemoglobin is 8.5 g/dL. The placenta is also hydropic, but microscopic examination of the placenta shows no inflammation of either fetal membranes or placental villi, and there is no meconium staining.

Which of the following mechanisms is the most likely explanation for these events?


A Maternal rubella infection in the first trimester

B A maternal chromosomal abnormality

C Maternal antibodies crossing the placenta

D Elevated maternal serum glucose

E Increased maternal phenylalanine levels

----------

Answer / Explanation:

[HIDE]

(C) CORRECT.

The hydrops and the icterus are findings of erythroblastosis fetalis, which is most often due to Rh blood factor differences between mother and fetus. The mother is exposed to Rh antigen in previous pregnancies and develops antibodies that cross the placenta in subsequent pregnancies to cause destruction of fetal red blood cells.[/HIDE]