Pathologic findings in pregnancies with unexplained increases in midtrimester maternal serum human chorionic gonadotropin levels.

Second trimester maternal serum human chorionic gonadotropin (MShCG) levels are commonly obtained as part of a screening protocol for chromosomal anomalies. Approximately 4% to 6% of patients have elevated hCG levels for gestational age, and this test has been reported to identify a group at risk for pregnancy complications. We ascertained 24 patients with unexplained elevated MShCG levels and available placental pathology among 5,790 deliveries during a 58-week period and compared them with 48 controls with normal MShCG levels delivering during the same period. Cases had a higher prevalence of preeclampsia, intrauterine growth retardation, and preterm delivery. Pathology in cases included more large-for-gestational-age placentas, fewer small-for-gestational-age placentas, lower mean fetoplacental weight ratios, more decidual plasma cell infiltrates, and more retroplacental hematomas. Other more frequent abnormalities that did not reach statistical significance included abnormal placental shape and chronic villitis. Maternal and fetal vascular abnormalities were similar in both groups. Morphometric analysis were performed on hCG-immunostained sections from placentas at 17, 21, 36, and 41 weeks' gestation. Patients with elevated MShCG showed an increased volume of hCG-positive trophoblast per unit surface area and increased intensity of hCG immunoreactivity within individual terminal villous units.