A longitudinal study of the relationship between placental and fetal growth as measured by ultrasonography.

Placental volume and fetal weight were estimated by ultrasonographic measurement at regular intervals from 16 to 20 weeks' gestation in 18 patients. The individual data were fitted to a logistic function. The estimated parameters were used to compare different groups of patients. In seven normal cases placental and fetal growth followed a sigmoid or nearly linear pattern. In four of these cases a reduction of placental and fetal growth during the last 1 to 3 weeks was apparent. In 11 cases with an abnormal outcome of pregnancy (fetal death, fetal distress necessitating a cesarean section, or neonatal weight below the 10th percentile) placental growth retardation always preceded fetal complications or growth retardation by at least 3 weeks.