To determine the utility of two-dimensional (2D) sonographic placental measurements in the prediction of small-for-gestational-age (SGA) infants.Methods
The maximal diameter along the fetal surface of the placenta and the maximal placental thickness were measured at 18–24 weeks' gestation, and the measurements repeated in the orthogonal plane. ‘Biometric lags’ were calculated as the difference between sonographic gestational age, estimated using each of a number of fetal biometric measurements, and actual gestational age. These variables were analyzed individually and in combination as predictors of birth weight < 10th percentile (SGA < 10) and < 5th percentile (SGA < 5).Results
1909 singleton pregnancies were included. Mean placental diameter (SGA < 10, P < 0.001; SGA < 5, P = 0.002) and thickness (SGA < 10, P < 0.006; SGA < 5, P = 0.065) were significantly smaller in SGA pregnancies. The biometric lags were greater in SGA pregnancies, the lag in abdominal circumference (AC) being the most predictive of SGA (P < 0.0001). Multivariable models were significantly predictive of both SGA < 10th percentile (area under the receiver–operating characteristics curve (AUC) = 0.7404) and < 5th percentile (AUC = 0.7204), the best fitting models including AC lag and mean placental diameter and thickness.Conclusions
2D placental measurements taken in mid-gestation are significantly associated with the incidence of SGA. Biometric lags can improve the predictive ability further. These easily obtained variables should be considered in future efforts to develop a clinically useful predictive model for adverse outcome of pregnancy.