To investigate the pathogenesis of pregnancies delivering small for gestational age (SGA) neonates by examining biochemical and Doppler indices of placental development during the first trimester of pregnancy.Method
The concentration of placental growth factor (PlGF) at 11+0-13+6 weeks was measured in 296 cases, which delivered SGA neonates, and 609 controls. The newborn was considered to be SGA if the birth weight was less than the fifth percentile after correction for gestation at delivery and sex, maternal racial origin, weight, height and parity. The distributions of uterine artery pulsatility index (PI), PlGF and PAPP-A, expressed in multiples of the median (MoM), in the control and SGA groups were compared. Logistic regression analysis was used to determine if significant contribution is provided by maternal factors, PlGF, PAPP-A and uterine artery PI in predicting SGA.Results
The median PlGF (0.900 MoM) and PAPP-A (0.778 MoM) were lower and uterine artery PI was higher (1.087 MoM) in the SGA group than in the controls (PlGF: 0.991 MoM; PAPP-A: 1.070 MoM; uterine artery PI: 1.030 MoM). In the SGA group there was a significant association between PlGF and PAPP-A (r = 0.368, p < 0.0001) and uterine artery PI (r = 0.191, p = 0.001). Significant contributions for the prediction of SGA were provided by maternal factors, PlGF and PAPP-A and with combined screening the detection rate was 27% at a false-positive rate of 5%.Conclusion
Birth weight is predetermined by placental development during the first trimester of pregnancy.