First and second trimester screening for large for gestational age infants.

Objectives: To find the best early predictor model for fetal growth and large for gestational age (LGA) infants considering clinical, ultrasonographic and biochemical variables.

Method: In 2097 singleton pregnancies at first trimester, we evaluated maternal characteristics, PAPP-A and ß-HCG proteins, fetal nuchal translucency thickness and uterine artery pulsatility index (UtA-PI). At second trimester fetal ultrasound biometry and UtA-PI were then measured. The relationships between birth weight and LGA and maternal characteristics, first and second trimester variables, and all variables combined, were studied. The performance of screening was determined by receiver operating characteristic curves analysis.

Results: Stepwise regression analysis showed that in the prediction of birthweight percentile there were significant contributions from all maternal factors, PAPP-A and Ut-A PI in the first trimester, and fetal biometric variables in the second trimester. Maternal charateristics combined with PAPP-A, β-hCG, fetal NT and uterine artery PI identified 30.2 % LGA (FPR 10%). The combined model reached a sensitivity of 41.2% (FPR 10%) and 56.2% (FPR 20%).

Conclusions: Sensitivity of the screening for LGA improves significantly after addition of second trimester ultrasound measurements to first trimester variables and maternal characteristics.