Ultrasonic evidence of placental calcification at 36 weeks' gestation: maternal and fetal outcomes.

Background: To determine the significance of an inappropriately mature placenta on ultrasound examination (Grannum classification), in a low-risk obstetric population. Scans were performed at 36 weeks' gestation. The study group comprised patients demonstrating a grade III placenta, and the control group comprised patients not demonstrating a grade III placenta.

Methods: A total of 1802 low-risk patients were scanned using serial directed real-time ultrasound at 36 weeks' gestation to determine placental maturity.

Results: The incidence of a grade III placenta at 36 weeks' gestation was 3.8% (68/1802). A grade III placenta was associated with young maternal age and cigarette smoking, p < 0.01. The incidence of proteinuric pregnancy-induced hypertension in the study and control groups was 7.4% (5/68) and 1.56% (27/1734), respectively, p < 0.01. The proportion of infants with a weight less than the 10th centile at birth in the study and control groups was 17.6% (12/68) and 5.6% (97/1734), respectively, p < 0.01.

Conclusions: Ultrasound detection of a grade III placenta at 36 weeks' gestation in a low-risk population helps to identify the "at-risk" pregnancy. It helps to predict subsequent development of proteinuric pregnancy-induced hypertension and may help in identifying the growth-restricted baby.