Correlation of ultrasonographic estimated fetal weight with actual birth weight in a tertiary hospital in Lagos, Nigeria

Sonographic Estimated Fetal Weight Within an Indian Cohort: Is the Hadlock Four Regression Model Appropriate or Does It Merit Adjustments?

Objective:

Sonographic estimated fetal weight (EFW) has an influence on the management of a pregnancy. The Hadlock 4 regression model (Hadlock-4), based on fetal biometry, is widely used. There are significant discrepancies noted between EFW, using Hadlock-4, compared to the actual infant birth weights (ABW) in the author’s clinical practice. The research objective was to compare the EFW, using Hadlock-4, with ABW and determine minor arithmetic modifications needed for this population.

Materials and Methods:

A prospective observational study was done enrolling women in the third trimester, who underwent sonography and delivered within a week of the examination. The sonographic cases were divided into class intervals by gestational age. The EFW were compared with the ABW, using a Pearson coefficient and mean percentage errors (MPE). The EFW values were increased or decreased, by a certain percentage, to keep the mean percentage error in an acceptable range.

Results:

The strength of association between the EFW and ABW was 0.69 ( p = .014). The EFW and the MPEs for women delivering at 36-40 weeks and beyond was significantly more (13.2 and 18.2%). The EFWs at 36-40 weeks and beyond 40 weeks were reduced by 3 and 8% respectively, which reduced the MPEs. After this modification 97.6% of ABWs fell within +/-2 standard deviations of the EFWs.

Conclusion:

A simple 3 and 8% reduction of EFWs, using the Hadlock-4, with those sonographic examinations at 36-40 weeks and beyond 40 weeks gestation respectively, is proposed to increase reliable in this Indian patient practice.

Prospective verification of sonographic fetal weight estimators among term parturients in Uganda

BACKGROUND

Accuracy 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.

METHODS

This 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.

RESULTS

The 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.

CONCLUSION

All 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.

Maternal and fetal characteristics to predict c-section delivery: A scoring system for pregnant women

INTRODUCTION

Cesarean section is one of the most common obstetrical interventions that has been performed at an increasing rate globally, due to both medical and non-medical reasons. This study aims to develop a prediction tool for pregnant women potentially needing c-section, such that necessary preparations from the mothers, families, and health providers can be made.

METHODS

A total of 603 pregnant women were recruited in the first phase of c-section prediction tool development. The association between the maternal and fetal factors on the risk of c-section were analyzed, followed by a stepwise multivariate regression analysis. In the next phase, 61 pregnant women were enrolled for external validation. Discrimination was assessed using area under the curve. The calibration plot was then made and assessed using the Hosmer-Lemeshow test.

RESULTS

There were 251 (41.6%) cases of vaginal delivery and 352 (58.4%) of c-section assessed. Multivariate analysis showed that gestational age < 37 wg (OR: 1.66, 95% CI: 1.10-2.51), pre-pregnancy body mass index (underweight) (OR: 0.40, 95% CI: 0.22-0.76), no history of vaginal delivery (OR: 2.66, 95% CI: 1.76-4.02), history of uterine surgery (OR: 8.34, 95% CI: 4.54-15.30), obstetrical complications (OR: 5.61, 95% CI: 3.53-8.90), birthweight ⩾ 3500 g (OR: 4.28, 95% CI: 2.16-8.47), and non-cephalic presentation (OR: 2.74, 95% CI: 1.53-4.89) were independently associated with c-section delivery. Those parameters were included in a 7-item scoring tool, with consecutive predictive scores of 1,-1,2,3,3,2,2,1. The area under the curve result was 0.813 (95% CI: 0.779-0.847), indicating a good predictive ability. The external validation showed AUC: 0.806, 95% CI: 0.694-0.917, Hosmer-Lemeshow test p = 0.666 and calibration plot coefficient of r = 0.939.

CONCLUSION

A total of 7 maternal-fetal factors were found to be strongly associated with c-section delivery, including gestational age < 37, maternal underweight body mass index, previous uterine surgery, obstetrical complications, birthweight ⩾ 3500, history of vaginal delivery, and non-cephalic presentation. Using these factors, a prediction tool was developed and validated with good quality.