# Detection rate of the Japan society of obstetrics and gynecology’s definition of fetal growth restriction for predicting small-for-gestational-age neonates

## TL;DR

This study compares two definitions of fetal growth restriction to see which better predicts small-for-gestational-age babies.

## Contribution

The study evaluates and compares the predictive accuracy of JSOG and SMFM definitions of fetal growth restriction in predicting SGA neonates.

## Key findings

- The JSOG definition had a higher positive likelihood ratio for predicting SGA neonates.
- The SMFM definition was more sensitive for identifying fetuses at risk of being SGA.
- Both definitions showed strong predictive power, but with differing strengths in sensitivity and likelihood ratios.

## Abstract

To identify the ability of the definitions of fetal growth restriction (FGR) according to the Japan Society of Obstetrics and Gynecology (JSOG) and the Society for Maternal–Fetal Medicine (SMFM) to predict small-for-gestational-age (SGA) neonates.

A retrospective cohort of Japanese women with singleton pregnancies who delivered at our hospital was analyzed. The primary outcome measure was the incidence of SGA neonates. The odds ratios (ORs) of SGA neonates according to the FGR definitions at 18 weeks (17–20 weeks, period 1) and 28 weeks (27–30 weeks, period 2) were calculated.

During periods 1 and 2, the incidence rates of SGA neonates were 7.6% and 7.7%, respectively. The ORs of the JSOG and SMFM definitions were 8.24 [95% confidence interval (CI) 4.27–14.4] and 5.88 (95% CI 3.90–8.88), respectively, during period 1 and 22.7 (95% CI 12.6–40.8) and 15.5 (95% CI 10.4–23.1), respectively, during period 2. Compared to the JSOG definition, the SMFM definition was more sensitive for predicting SGA neonates. During both periods, the positive likelihood ratio (LR +) of the JSOG definition was higher than that of the SMFM definition for predicting SGA neonates.

The JSOG definition more strongly predicts SGA neonates and is associated with a higher LR + . The SMFM definition is highly sensitive for screening fetuses at risk for SGA status.

The online version contains supplementary material available at 10.1007/s10396-025-01551-2.