EP08.11: Prenatal ultrasound for fetal growth assessment in obese women

We aimed to find the accuracy and predictive value of third trimester ultrasound (US) to detect fetuses with abnormal growth in obese women who deliver at term. This was a prospective cohort study performed in the Emergency University Hospital of Craiova Prenatal Diagnosis Unit (Project Code 142081 - European Social Fund). We enrolled obese women with singleton fetuses having a growth ultrasound (US) performed 1 day to 4 weeks before delivery. Fetuses with a US estimated fetal weight (EFW) >90% (large for gestational age – LGA) or <10% (small for gestational age - SGA) based on the Hadlock-4 formula were included. For neonates we used reference data from INTERGROWTH-21(st) Project and the omnicalculator. We analysed three classes of obese patients: body mass index (BMI) of 30 to <35, BMI of 35 to <40 and BMI of 40 or higher. We compared the area under the curve for receiver-operating characteristic (ROC) curves in the three classes. We performed a test for an equal variance to compare the EFW percentile and birth percentile in both groups. We assumed an equal variation at p value > 0.05. We screened 3380 patients and enrolled 541 eligible women. Abnormal values of EFW were found in 118 fetuses (21.81%). 16 (2.95%) fetuses had a Hadlock-4 EFW <10%, and 102 (18.85%) - an EFW >90%. The corresponding postnatal weight was confirmed in 17, respectively in 94 newborns in these two groups. In the SGA group, the EFW percentile was similar to the birth percentile. For the LGA group, we found a significant standard deviation difference (unequal variance), as the p-value for Levene's test was less than 0.05 (p = 0.01). The ROC curves did not differ significantly for different classes of obesity. Third trimester US in obese women who deliver at term has a higher accuracy in detecting SGA fetuses. In the LGA group, the EFW percentile is more likely to differ from the birth percentile.