Increased abdominal circumference as predictor of macrosomia without evidence of adverse obstetrical or neonatal outcomes

Abstract

Ultrasound is used as a screening tool for suspected fetal macrosomia, primarily focused on estimated fetal weight (EFW). The interpretation of isolated increased abdominal circumference (AC), however, is unclear. We aimed to determine if increased AC alone, in the setting of normal EFW and the absence of diabetes, is associated with any adverse obstetric or neonatal outcomes. This is a secondary analysis of a prospective observational study of individuals with negative diabetes screening between 2016-2020. Third trimester ultrasound data was examined to develop our study group (AC ≥ 95%tile, EFW< 95%tile) and comparison group (AC< 95%tile, EFW< 95%tile). Obstetric (induction, shoulder dystocia, primary Cesarean rate, postpartum hemorrhage) and neonatal (large for gestational age (LGA) phototherapy, hypoglycemia, NICU admission) outcomes were compared using chi-square analyses. We performed logistic regression to evaluate which antepartum factors may be most predictive of AC ≥ 95%tile and created ROC curves with gestational weight gain (up to 28weeks) and glucose tolerance testing (GTT). A total of 1239 individuals were included in the study population. Those with AC ≥ 95%tile (n = 40) had an increased rate of LGA (17% vs 2.4%, p< 0.001). There were no differences between rates of induction, shoulder dystocia, primary Cesarean, postpartum hemorrhage, phototherapy, neonatal hypoglycemia, or NICU admission (Table 1). Using logistic regression, weight gain and GTT values were found to be significant in predicting AC ≥ 95%tile. ROC curves were developed, the better model being GTT (AUC 0.637), suggesting a 1 hour GTT > 105 may be predictive of AC ≥ 95%tile (Figure 1). AC ≥ 95%tile was associated with macrosomia, but not with other adverse obstetric/neonatal outcomes. Additionally, a 1 hour GTT > 105, while normal, seems to be a risk factor for AC ≥ 95%tile and should be considered indication for a third trimester growth scan. Further studies are needed to determine if antepartum surveillance should be recommended in this population.View Large Image Figure ViewerDownload Hi-res image Download (PPT)