Small for gestational age at preterm birth identifies adverse neonatal outcomes more reliably than antenatal suspicion of fetal growth restriction

Abstract

Background

Fetal growth restriction (FGR) is an important reason for premature delivery and a leading cause of perinatal morbidity and mortality. We aimed to evaluate whether classification as small for gestational age (SGA; <10^th centile) at birth or antenatal suspicion of FGR was more strongly associated with neonatal morbidity and mortality in preterm infants.

Methods

A retrospective audit of infants born between 24 + 0 and 32 + 6 weeks of gestation from 2012–2019 and admitted to the Neonatal Unit at Mercy Hospital for Women (MHW). Infants were categorized according to whether FGR was listed as an antenatal complication in the medical records and whether they were SGA (<10^th centile on Fenton chart) or appropriate for gestational age (AGA) at birth, and comparisons for neonatal outcomes were made.

Results

371/2126 preterm infants (17.5%) had antenatal suspicion of FGR, and 166 (7.8%) were SGA at birth. No differences in any neonatal outcomes were found between infants with or without suspected FGR, except decreased intraventricular hemorrhage (IVH) in the FGR group. SGA classification was associated with increased rates of all morbidities other than IVH, including bronchopulmonary dysplasia, retinopathy of prematurity, and necrotizing enterocolitis, compared with the AGA group. Death was significantly higher in the SGA group (7.2%) compared with the AGA group (3.5%).

Conclusion

SGA by Fenton chart more reliably identified neonates at risk of adverse neonatal outcomes than antenatal suspicion of FGR, suggesting it is a reasonable clinical proxy. This most likely reflects the much lower tenth centile weight cutoffs on the Fenton charts compared to in-utero charts used antenatally to diagnose FGR based on ultrasound estimated fetal weight. SGA classification by Fenton approximately equates to <3^rd centile on in-utero charts at our institution, therefore identifying the most severe FGR cases.

Keywords:

• Fetal growth restriction
• small for gestational age
• neonatal morbidity
• neonatal mortality

Acknowledgements

We thank the data managers of the Neonatal Department at Mercy Hospital for Women for assisting in conducting this study.

Disclosure statement

The authors declare they have no conflict of interest to disclose.

Data availability

The data supporting this study’s findings are available from the corresponding author, [MGA], upon reasonable request.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.