Placental size during early pregnancy and fetal outcome: a preliminary report of a sequential ultrasonographic study.

Placental growth during pregnancy was studied serially by ultrasonographic measurement of placental area in 50 primigravid women. Placental area at a menstrual age of 150 days was compared to infant birth weight. Small placental area at a menstrual age of 150 days was significantly related to low infant birth weight (< tenth percentile of birth weight for gestational age). A "warning limit" of placental area at midpregnancy was calculated. If placental area was equal to or smaller than this limit of 187 sq cm, six of nine patients (67%) compared to four of 41 subjects with larger placentas (p < 0.01) were delivered of a small-for-gestational age baby. Ultrasonographic placental area measurement in midpregnancy thus appears to be of prognostic value in identifying pregnancies at high risk for the subsequent occurrence of fetal growth.