Second trimester contingent screening for small for gestational age neonates.

First, to investigate the additive value of second trimester placental growth factor (PlGF) for the prediction of small for gestational age (SGA) neonates. Second, to examine second trimester contingency screening strategies. This is a prospective observational study in 40,241 women with singleton pregnancies undergoing routine ultrasound examination at 19 - 24 weeks' gestation. We used the competing risks model for prediction of SGA. The parameters for the prior model and the likelihoods for estimated fetal weight (EFW) and uterine artery pulsatility index (UtA-PI) were those presented in previous studies. A folded plane regression model was fitted in the dataset of this study to describe the likelihood of PlGF. We compared the prediction of screening by maternal risk factors and EFW against the prediction provided by a combination of maternal risk factors EFW, UtA-PI and PlGF. We also examined the additive value of PlGF in a policy that uses maternal risk factors, EFW and UtA-PI. Overall, the prediction of SGA improved for increasing degree of prematurity, for higher severity of smallness and for coexistence of preeclampsia. The combination of maternal risk factors EFW, UtA-PI and PlGF improved significantly the prediction provided by maternal risk factors and EFW for all the examined cut-offs. Screening by a combination of maternal risk factors plus serum PIGF improved the prediction of SGA when compared to screening by maternal risk factors alone. However, the incremental improvement in prediction was decreased when PIGF was added to screening by a combination of maternal risk factors, EFW, and UtA-PI. If first line screening for SGA neonates with birth weight <10 percentile delivered at <37 weeks' gestation was by maternal risk factors and EFW, the same detection rate of 90% at overall FPR of 50% achieved by screening with maternal risk factors EFW, UtA-PI and PlGF of the whole population can be achieved by reserving the measurements of UtA-PI and PlGF to only 80% of the population. Similarly, in screening for SGA with birth weight <10 percentile delivered at <30 weeks the same detection rate of 90% at overall FPR of 14% achieved by screening with maternal risk factors EFW, UtA-PI and PlGF of the whole population can be achieved by reserving the measurements of UtA-PI and PlGF to only 70% of the population. The additive value of PlGF in reducing FPR to about 10% with a simultaneous detection rate of 90% for SGA <3 percentile born <30 weeks, is gained by measuring PlGF in only 50% of the population. The combination of maternal risk factors, EFW, UtA-PI and PlGF provide effective second trimester prediction of SGA. Serum PlGF is useful for predicting SGA <3 percentile born