Severity of fetal growth restriction stratified according to maternal obesity

Abstract

Objective

The primary objective of this study was to ascertain if among women with fetal growth restriction (FGR; estimated fetal weight [EFW] < 10th percentile) the frequency of severe FGR (sFGR; EFW < 3rd percentile for gestational age) differed among various classes of obesity.

Study design

This was a retrospective cohort study of all pregnancies complicated by FGR from August 2016- March 2019 at a single center, undergoing weekly antenatal surveillance (biophysical profiles and umbilical artery Doppler). Exclusion criteria included multiple gestation, prenatally diagnosed fetal anomalies, and unknown maternal body mass index (BMI) at the time of the ultrasound exam. We defined fetal growth restriction as an estimated fetal weight less than the 10th percentile for gestational age using Hadlock criteria. Severe FGR was defined as the estimated fetal weight below 3rd percentile for gestational age. Maternal BMI was categorized as non-obese (BMI ≤ 29.9), Class I obesity (30.0–34.9), and Class II or III obesity (≥35.0 kg/m²). Abnormal Dopplers were defined as absent or reversed end diastolic flow. Maternal characteristics and ultrasound findings were compared between groups. Categorical variables were compared by χ² or Fisher’s exact test and continuous variables were compared by t test or nonparametric Wilcoxon rank sum test. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals by adjusting for potential confounders including maternal age, hypertensive disorders, pre-gestational and gestational diabetes, auto-immune disorders, and gestational age at diagnosis.

Results

Of 974 women that met the inclusion and exclusion criteria, 678 (70%) were not obese, 151 (15%) had class I obesity, and 145 (15%) had class II or III obesity. Obese women were significantly more likely to be multiparous and had a lower mean gestational age at diagnosis of FGR. Hypertensive disorders were more common with increasing BMI, as was type II diabetes mellitus (p < .01). There were no statistically significant differences between the obesity groups with regards to other comorbidities. Women with obesity classes I and II/III had significantly higher frequency of severe FGR (37.8%) as compared to non-obese women (29%; p < .05). The rates of abnormal Dopplers was more frequent with worsening obesity: 31.4%, 34.4%, and 46.2% for non-obese, class I obesity, and class II or III obesity, respectively (p < .01). There were no significant differences in amniotic fluid abnormalities or antenatal testing results. After adjustment for potential confounders, women with class I obesity had higher odds of having severe FGR (aOR = 1.4; 95% CI = 1.0–2.1). There was also an increased odds of abnormal Dopplers among women with class II/III obesity, as compared to non-obese women, after adjusting for confounders (aOR = 1.7; 95% CI = 1.2–2.6).

Conclusion

Among women with FGR, obese women were more likely to have severe FGR and abnormal Dopplers compared to non-obese women. These findings warrant further study into predictors of adverse outcomes among obese women with FGR. Such information could be useful in counseling patients as to the possible course of disease after diagnosis of fetal growth restriction.

Keywords:

• Fetal growth restriction
• obesity
• ultrasound
• antenatal testing

Disclosure statement

No potential conflict of interest was reported by the author(s).