Fetal abdominal wall defects in an Australian tertiary setting: contemporary characteristics, ultrasound accuracy, and outcome

Estimating fetal weight in gastroschisis: A 10 year audit of outcomes at the National Maternity Hospital

OBJECTIVE

To identify whether conventional methods of estimating fetal growth (Hadlock's formula), which relies heavily on abdominal circumference measurements, are accurate in fetuses with gastroschisis.

METHODS

A retrospective cohort study was performed between the period January 1, 2011 and December 31, 2021 in a tertiary referral maternity hospital identifying all pregnancies with a diagnosis of gastroschisis. Projected fetal weight was obtained using the formula (EFW [Hadlock's formula] + 185 g × [X/7]) where X was the number of days to delivery.

RESULTS

During the study period 41 cases were identified. The median maternal age was 25. The median BMI was 25 and 63% were primiparous women (n = 26). Median gestation at diagnosis was 21 weeks. Median gestation at delivery was 36 weeks. A total of 4.8% of mothers had a history of drug use (n = 2). The rate of maternal tobacco use was 21.9% (n = 9). A total of 4.8% of fetuses had additional congenital anomalies including amniotic band syndrome and myelomeningocele (n = 2). Estimated fetal weight (EFW) and birth weight data were available for 34 cases. A Wilcoxon signed-rank test showed projected EFW using Hadlock's formula did not result in a statistically significant different birth weight (Z = -1.3, P = 0.169). Median projected weight and actual birth weight were 2241.35 and 2415 g respectively. Median difference was 0.64 g (95% CI: -148 to -28.5).

CONCLUSION

Our data showed accuracy using standard formulae for EFW in fetuses with gastroschisis.

Correlation between estimated fetal weight and weight at birth in infants with gastroschisis and omphalocele

BACKGROUND

An accurate estimated fetal weight (EFW) calculated with traditional formulae in cases of abdominal wall defects (AWDs) can be challenging. As a result of reduced abdominal circumference, fetal weight may be underestimated, which could affect prenatal management. Siemer et al. proposed a formula without the use of abdominal circumference, but it is not used in our protocols yet.

OBJECTIVES

Our aim was to evaluate the correlation of EFW and birth weight in fetuses with AWD by using Hadlock 1, Hadlock 2, and Siemer et al.'s formulae. Our secondary goal was to evaluate how often fetuses classified as small for gestational age (SGA) were in fact SGA at birth.

STUDY DESIGN

This was a retrospective cohort study of gestations complicated by gastroschisis and omphalocele at two tertiary-care centers in Brazil and Italy during an 8-year period. Of a total of 114 cases, 85 (44 cases of gastroschisis and 41 cases of omphalocele) met our criteria.

RESULTS

The last prenatal scan was performed 5.2 (±4.1) days before birth. The mean gestational age at birth was 37.2 (±1.8) weeks. Correlation of EFW with birth weight was calculated with the three formulae with and without adjustment for weight gain between scan and birth, with the use of the Spearman coefficient. The correlation between EFW and weight at birth was positive according to all three formulae for the infants with gastroschisis. This finding was not confirmed in the infants with omphalocele. All formulae overestimated the number of SGA cases: although only 17.6% of fetuses were actually SGA at birth, the Hadlock formulae had classified nearly 35% of them as SGA, and Siemer et al.'s formula, 15.3%.

CONCLUSION

All three formulae yielded a good correlation between EFW in the last scan and birth weight in the infants with gastroschisis but not for those with omphalocele. Cases of SGA were overestimated.

Accuracy of sonographic estimation of weight in fetuses with abdominal wall defects

BACKGROUND

Accurate estimation of fetal weight is essential in guiding management of fetuses with abdominal wall defects (AWDs), as growth restriction is an important predictor of perinatal morbidity and mortality. Several sonographic formulae are available involving multiple biometric parameters, but abdominal circumference measurements may underestimate weight in fetuses with AWDs. No formula has yet shown superior accuracy.

AIMS

The objectives of this study were to evaluate, in fetuses with gastroschisis and omphalocoele, the accuracy of a sonographic estimated fetal weight (EFW) formula proposed by Siemer and colleagues, specifically for use in fetuses with AWDs compared to the commonly used Hadlock IV formula in estimating fetal weight, and detecting small for gestational age (SGA) fetuses.

MATERIALS AND METHODS

A retrospective cohort of 113 fetuses with AWDs was identified from an Australian teaching hospital over 13 years. Pregnancy data and sonographic fetal biometry parameters were obtained. The accuracy of each formula in predicting birthweight was compared using Bland-Altman limits of agreement, and the intraclass correlation coefficient between EFW and actual birthweight. Performance of each formula in detecting SGA fetuses was determined.

RESULTS

The Siemer and Hadlock formulae have similar accuracies for predicting birthweight in fetuses with AWDs. The Hadlock formula has a higher detection rate for SGA < 10^th centile and < 3^rd centile compared to the Seimer formula (84% vs 68% and 83% vs 67% respectively), albeit with a higher false-positive rate.

CONCLUSION

There is no clear clinical advantage in using the Siemer formula, which is specifically designed for fetuses with AWDs, over the Hadlock formula to estimate weight in fetuses with AWDs.