Accuracy of third trimester ultrasound in predicting neonatal birthweight in patients with inflammatory bowel disease

OBJECTIVE

To evaluate the accuracy of third trimester ultrasound in predicting birthweight in patients with inflammatory bowel disease (IBD) using the gestation-adjusted projection (GAP) method.

STUDY DESIGN

Retrospective cohort study including pregnant patients with IBD who had third trimester ultrasounds and delivered at a single institution from 2012 to 2017. Controls included pregnant patients without IBD seen during the study period with third trimester ultrasounds. Correlation plots of GAP birthweight and actual birthweight (AB) were created for IBD-positive cases, IBD-negative controls, and IBD-positive cases with and without prior abdominal surgery. GAP predicted birthweight error was calculated for cases and controls. Univariable linear regression models estimated the association between predicted birthweight and AB. Multivariable linear regression models estimated the association between GAP birthweight and AB adjusting for age, BMI, race, and IBD status.

RESULTS

320 patients were included (172 cases and 148 controls). Cases were more likely to be older (p < 0.001), white (p < 0.001), and have a lower BMI (p = 0.001). Correlation plots of GAP birthweight and AB showed linear correlations in cases (Spearman ρ = 0.81), controls (ρ = 0.74), cases with (p = 0.78) and without prior surgery (ρ = 0.83). GAP birthweight was significantly associated with AB in controls and cases in univariable linear regression models (β = 0.85, standard error = 0.04, p < 0.001; β = 0.90, standard error = 0.06, p < 0.001, respectively). No significant difference was found between the parameter estimates of the two models (p = 0.47). GAP birthweight remained significantly associated with AB in a multivariable linear regression model (β = 0.86, standard error = 0.03, p < 0.001). There were no significant differences between GAP predicted birthweight error between controls and cases (APE 11% vs 10% respectively, p = 0.56) and between cases without and with prior surgery (APE 10% vs 11%, p = 0.7).

CONCLUSION

The accuracy of fetal biometry in the third trimester for predicting actual birthweight was equivalent between patients with and without IBD and those with prior abdominal surgery.

Accuracy of sonographic fetal weight estimation within 14 days of delivery in a Jordanian population using Hadlock formula 1

OBJECTIVES

To assess the accuracy of sonographic fetal weight estimation within 14 days of delivery in a Jordanian population using Hadlock formula 1 in the third trimester.

MATERIALS AND METHODS

Estimated fetal weights and actual fetal weights data were collected from the medical records of pregnant women who had undergone sonographic fetal weight estimation within 14 days of delivery over the period of March 2008 to June 2010. The analysis included 409 Jordanian women; 6 of them had twins, so the study involved estimation of 415 fetal weights, and these were compared to the actual recorded neonatal weights. Using Hadlock formula 1, we compared the estimations with the infants' actual birth weights. The data were analyzed in 2 groups: within 7 days and 8-14 days.

RESULTS

The mean estimated fetal weight was 3,133 ± 475 g (range 1,343-4,420 g). The mean actual birth weight was 3,179 ± 450 g (range 1,300-4,450 g). The mean absolute percentage of error of ultrasound fetal weight estimation for all infants was 6.5%; however, it was 6.1 and 8.2% if the fetus was delivered within 7 days or 8-14 days of sonography, respectively. Overall, 78.8% of fetal weight estimations were within 10% of actual birth weight; however it was 81.3 and 69.9% if the fetus was delivered within 7 days or from 8-14 days of sonography, respectively.

CONCLUSION

The use of Hadlock formula 1 for sonographic fetal weight estimations in Jordanian women showed acceptable results relative to the actual neonatal weight at birth. However, fetal weight estimation was more reliable when performed within 7 days of delivery.