Serial human placental lactogen estimations in serum and placental weight-for-dates.

The relation between serial HPL assays in serum and placental weight-for-dates was studied in 70 randomly chosen pregnant women. Out of five different aspects of the HPL curve only a fall below the 2-3d centile without subsequent recovery was related to low placental weight. When a small-for-dates (SFD) placenta was associated with normal HPL levels, maternal body weight tended to be lower than if both placental weight and HPL levels were abnormal. This suggests that physiologically small placentae are discernible from pathologically small placentae by a normal HPL curve.