To determine if, in pregnant obese women, prenatal ultrasonography (US) can accurately predict abnormal birthweight (BW) in newborns.METHODS:
We conducted a retrospective chart review of singleton deliveries of obese women between January 1, 2014 and March 31, 2015 at UVA. IUGR was defined as an EFW <10% while LGA was defined as EFW > 90%. BW was categorized into normal (2500-3999 grams), low (<2500 grams), and macrosomic (≥4000 grams). Chi squared tests and logistic regression were used for analyses.RESULTS:
We included 307 women in our study. Indicated third trimester growth US for chronic hypertension or diabetes occurred among 17.6% (54/307) of women. Among the remaining women without these indications, 70.4% (178/253) had at least one follow up US. Overall, 22.3% (44/197) of newborns had a discordant prenatal EFW and BW. For macrosomic infants, 13.9% (5/36) were LGA prenatally, while 58.33% (21/36) appeared normal. Among low BW (LBW) newborns, 13.2% (5/38) had IUGR prenatally, while 44.8% (17/38) had a normal EFW. Normal BW infants were rarely diagnosed as IUGR (1/232, 0.5%) or LGA (5/232, 2.2%). A BMI 35-40 (OR=0.41, 95%CI: 0.18-0.96), having 2-3 US (OR=0.31, 95%CI: 0.12-0.76), and diabetes (OR=0.41, 95%CI: 0.18-0.94) reduced the odds of predicting LBW and macrosomia.CONCLUSION:
In obese women, there is a high rate of discordance between prenatal fetal growth abnormalities and actual BW. Having a higher BMI or another comorbidity reduces the accuracy of predicting abnormal BW. Prenatal prediction of LBW or macrosomia does not improve after the first follow up growth US.