Abstract
BackgroundAccuracy of fetal weight estimation by ultrasound is essential in making decisions on the time and mode of delivery. There are many proposed formulas for fetal weight estimation such as Hadlock 1, Hadlock 2, Hadlock 3, Hadlock 4 and Shepard. What best applies to the Ugandan population is not known since no verification of any of the formulas has been done before. The primary aim of this study was to determine the accuracy of sonographic estimation of fetal weight using five most commonly used formulas, and analyze formula variations for different weight ranges.MethodsThis was a hospital based prospective cohort study at Mulago National Referral Hospital, Kampala, Uganda. A total of 356 pregnant women who consented and were within 3 days of birth were enrolled. Prenatal ultrasound fetal weight determined by measuring the biparietal diameter, head circumference, abdominal circumference, femoral length, and then was compared with actual birth weight.ResultsThe overall accuracy of Hadlock 1, Hadlock 2, Hadlock 3, Hadlock 4 and Shepard formula were 66.9, 73.3, 77.3, 78.4 and 69.7% respectively. All Hadlocks showed significant mean difference between weight estimates and actual birth weight (p < 0.01) whereas Shepard formula did not [p - 0.2], when no stratification of fetal weights was done. However, all Hadlocks showed a none significant (p-values > 0.05) mean difference between weight estimates and actual birth weight when the actual birth weight was ≥4000.0 g. Shepard weight estimates showed a none significant mean difference when actual birth weight was < 4000 g. Bland-Altman graphs also showed a better agreement of weight estimated by Shepard formula and actual birth weights.ConclusionAll the five formulas were accurate at estimating actual birth weights within 10% accuracy. However, this accuracy varied with the fetal birth weight. Shepard was more accurate in estimating actual birth weights < 4000 g whereas all Hadlocks were more accurate when the actual birthweight was ≥4000 g.
Highlights
Accuracy of fetal weight estimation by ultrasound is essential in making decisions on the time and mode of delivery
A total of 365 parturients were recruited in the study, 3 fetuses had congenital anomalies and 6 of the fetuses had a Biparietal Diameter (BPD) ≥10 cm, and Shepard failed to calculate the fetal weight estimation and was removed from this study, remaining 356 leading to a completion rate of 99.2%
The maternal body mass index (BMI) in majority of the parturients were within the normal range (57.3%)
Summary
Accuracy of fetal weight estimation by ultrasound is essential in making decisions on the time and mode of delivery. Maternal and infant mortality is a major public health issue globally and in Uganda. In 2017, an estimated 295, 000 women died during and following pregnancy and child birth, as a vast majority of these deaths (94%) occurred in low resource setting. Sub-Saharan Africa alone accounted for approximately two-third (196,000) of maternal deaths and 6.000 of these cases were from Uganda [1]. Antenatal care reduces both maternal and infant morbidity and mortality and prenatal fetal weight estimation is known to be an important component of standard antenatal care. Maternal risks associated with the delivery of an excessively big fetus include birth canal and pelvic floor injuries, as well as postpartum hemorrhage [3]
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