Longitudinal study of individually adjusted fetal growth.

Objective: To construct individualized fetal growth curves estimated by ultrasound parameters adjusted for maternal and fetal characteristics.

Methods: Data were retrospectively assessed from serial ultrasonographic examinations of singleton pregnancies at 12-42 gestational weeks among women without maternal or fetal conditions and full-term delivery at the University Hospital of University of São Paulo between July 1, 2014, and December 31, 2017. Measurements included biparietal diameter, head circumference, abdominal circumference, and femur length. Mixed linear regression was used to model the ultrasound biometric parameters as a function of gestational age, parity, maternal height, pre-pregnancy weight, and fetal sex.

Results: In total, data were assessed from 1445 examinations of 434 pregnancies meeting the inclusion criteria. The estimated fetal weight model included gestational age, fetal sex, maternal height, and pre-pregnancy body mass index as covariates. The model enabled the construction of individual estimated fetal weight curves with respective percentiles covering 12-42 gestational weeks using maternal and fetal characteristics.

Conclusion: The growth curves, which are based on a sample of the Brazilian population with low risk of maternal or fetal morbidity and mortality, will make it possible to determine whether a fetus is achieving ideal growth potential according to maternal and fetal characteristics.