Greater estimated fetal weight and birth weight in IVF/ICSI pregnancies after thawed as compared with fresh blastocyst transfer: prospective cohort study with novel unified modeling methodology.

Robust novel unified prenatal-postnatal modelling in IVF/ICSI pregnancies after thawed or fresh BT from 19 weeks to birth showed non-divergent growth trajectories with greater EFW and BW Z-scores in frozen vs. fresh BT. Mean EFW Z-scores in both IVF/ICSI groups were greater as expected for natural conception up to 32 weeks in fresh BT and 35 weeks in thawed BT, with maximum effect at mid-trimester, decreasing with advancing gestation. Mean BW Z-scores were negative in both groups, with lower values in premature fetuses and increasing with advancing gestation. IVF/ICSI conceptions from thawed as compared to fresh BT present increased rate of LGA and reduced rate of SGA both prenatally or postnatally. The proportion of SGA fesuses across gestation increases rapidly in fresh and smoothly in thawed, whereas that of LGA fetuses decreases rapidly in thawed vs smoothly in fresh. Prediction models of SGA-LGA may be improved considering: 1. mode of conception with use of blastocyst cryopreservation; 2.unified prenatal-postnatal curves; 3. greater efficiency of prenatal prediction of SGA for fresh and for LGA in thawed. This article is protected by copyright. All rights reserved.