Fetal abdominal circumference and adverse perinatal outcomes in pregnant individuals with pregestational diabetes.

BACKGROUND

Disturbances in fetal growth (ie, growth restriction and macrosomia) are associated with increased risk of perinatal morbidity and mortality. Although fetal abdominal circumference (AC) was recently added to the definition of fetal growth restriction, less is known about the performance of small AC specifically among pregnant individuals with diabetes as well as the clinical utility of large AC. Thus, we aimed to evaluate the association between fetal AC and adverse outcomes in pregnant individuals with pregestational DM.

STUDY

DESIGN

This was a retrospective cohort study of pregnant individuals with pregestational DM who delivered a non-anomalous, singleton gestation at a tertiary care center from January 2012-January 2022. Pregnant individuals without fetal AC measurement within 4 weeks of delivery were excluded. The primary outcome was composite perinatal morbidity including 1 or more of: neonatal hypoglycemia, neonatal hyperbilirubinemia, preterm birth, shoulder dystocia, stillbirth or neonatal death. Baseline characteristics and outcomes were compared by fetal AC percentile on last ultrasound before delivery: <10th percentile (small), 10-90th percentile (normal), and >90th percentile (large) for gestational age. Multivariable regression estimated the association between small and large AC and outcomes, compared with normal AC. Sensitivity analyses were performed defining AC using <5th and >95th percentile cutoffs and separately restricting the population to only those with normal EFW on ultrasound to evaluate the effect of isolated small and large AC.

RESULTS

Of 1,178 pregnant individuals included: 127 (11%) had small AC, 704 (60%) had normal AC, and 347 (29%) had large AC. Composite perinatal morbidity occurred more often in pregnant individuals with small AC (72%) and large AC (71%), compared with those with normal AC (60%), p<.001). Large AC was associated with higher adjusted odds of composite perinatal morbidity (aOR 1.80, 95% CI 1.32-2.45), compared with normal AC. Small AC was not significantly associated with composite morbidity (aOR 1.22; 95% CI 0.76-1.97) but was associated with higher odds of preterm birth, severe perinatal morbidity, mechanical ventilation, stillbirth and SGA. Large AC was also associated with higher odds of neonatal hypoglycemia, NICU admission, cesarean and LGA. In sensitivity analyses using AC definitions <5th and >95th, the findings were similar with greater magnitude of association. When evaluating only individuals with normal EFW, isolated large AC >90th was associated with higher odds of perinatal morbidity and shoulder dystocia, whereas isolated small AC <10th was only associated with cesarean and SGA.

CONCLUSION

Abnormal fetal AC was consistently associated with higher odds of perinatal morbidity and mortality regardless of fetal AC definition and overall EFW, suggesting that fetal AC may provide additional important clinical information about the developing fetus. Future studies are needed to determine if abnormal fetal AC should be used to guide management in pregnant individuals with pregestational DM.