A united states national reference for fetal growth

TLDR

The study aims to create a contemporary national fetal growth curve to serve as a standard reference for research on small and large for gestational age outcomes. Using 3,134,879 live births from 1991, the authors developed the curve, compared it to four prior curves, and applied methods to correct implausible birth weight–gestational age pairs and smooth the curve across gestational ages. The new curve shows that earlier curves underestimated US fetal growth, especially at 33–38 weeks, leading to markedly different fetal growth restriction prevalence and rendering older curves obsolete for current birth weight distribution and FGR assessment.

Abstract

To develop a current national fetal growth curve that can be used as a common reference point by researchers to facilitate investigations of the predictors and consequences of small and large for gestational age delivery. Single live births to United States resident mothers in 1991 (n = 3,134,879) were used for the development of this curve, which was compared with four previously published fetal growth curves. Techniques were developed to address cases with implausible birth weightgestational age combinations and to smooth fetal growth curves across gestational age categories. In general, the previously published fetal growth curves underestimated the 1991 United States reference curve. This underestimation is most apparent during the latter weeks of gestation, approximately 33–38 weeks. Our findings indicate that the prevalence of fetal growth restriction (FGR) will vary markedly, depending on the fetal growth curve used. Furthermore, many previously published fetal growth curves no longer provide an up-to-date reference for describing the distribution of birth weight by gestational age and for determining FGR that is consistent with the most recent live birth data for the entire United States.