Reliability of a clinical method in estimating foetal weight and predicting route of delivery in term parturient monitored at a voluntary agency hospital in Southwest Nigeria

BACKGROUND

The antepartum estimation of foetal weight is a major determinant of the route of delivery and this has become vital in modern day obstetrics. The limitations to the use of obstetric ultrasonography, considered as the gold standard in estimating foetal weight, make clinical estimation methods attractive alternatives, especially in resource- constrained settings where many un-booked women may report for delivery.

AIM

To determine the reliability of intrapartum clinical foetal weight estimation in predicting the actual birth weight (ABW) and route of delivery among term parturient.

SETTING

The study was conducted at the Sacred Heart Hospital, Lantoro, a voluntary mission agency hospital in Southwest Nigeria.

METHODS

This cross-sectional study was conducted among 291 term parturient recruited by systematic random sampling between June and September 2017. The clinical estimation of foetal weight was carried out using Johnson's formula.

RESULTS

The accuracy of Johnson's formula to predict the ABW was 59.5%; while for the mode of delivery, it was 130 (75.1%) for spontaneous vaginal delivery (SVD) and 43 (24.9%) for caesarean section (CS). The sensitivity of the accuracy of Johnson's formula to predict the mode of delivery was 75.1%, with a specificity of 35.6%, a positive predictive value (PPV) of 63.1%, and a negative predictive value (NPV) of 49.4%.

CONCLUSION

The intrapartum clinical foetal weight estimation at term determined by Johnson's formula was reliably predictive of ABW and SVD, but it was unreliable in predicting the need for a CS.

Estimation of fetal weight: a comparison of clinical and sonographic methods

Fetal weight estimation is important in the management of labour and delivery. This study aimed to compare the accuracy of the clinical and ultrasound methods of fetal weight estimation. This was a prospective study involving 110 term cephalic singleton pregnancies delivered within 24 hours of clinical fetal weight estimation using Johnson's and Dare's formulae and ultrasound estimation at a Tertiary hospital in Abakaliki, Nigeria. The data were analysed with Stata 11 software. The sonographic estimation within 10% of the actual birth weight (ABW) of 68.2% was significantly greater than the accuracy of Johnson's (23.6%), Dare's (26.4%), and the combined clinical formulae (27.1%). The clinical methods overestimated the fetal weight. Both methods showed a positive correlation with the ABW. In conclusion, the sonographic method had a better accuracy than the clinical methods. However, fetal weight overestimation by clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude fear of complications from macrosomia. Impact statement What is already known on this subject? An accurate estimation of fetal weight is important in the management of labour and delivery. However, there is limited evidence that any of the available methods of fetal weight estimation is more accurate than the others. What do the results of this study add? This study showed that the clinical methods using Johnson's and Dare's formulae had a significantly higher mean percentage and absolute mean percentage error compared to the sonographic estimation of fetal weight. The sonographic estimation within 10% of actual birth weight (ABW) of 68.2% was significantly greater than that of Johnson's and Dare's formulae with 23.6% and 26.4%, respectively. All of the methods showed a positive correlation with the ABW. What are the implications of these findings for clinical practice and/or further research? This implies that the sonographic method has a better accuracy than the clinical methods in estimating the fetal weight. However, the overestimation of fetal weight by the clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude the fear of complications from macrosomia.

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

BACKGROUND

Sonographic fetal weight estimation is an important component of antenatal care.

AIM

To sonographically estimate fetal weight at term and to compare estimated with actual birth weights to determine the validity of estimated fetal weights.

SUBJECTS AND METHODS

In the prospective study, a convenience sample of 282 women was recruited. Ethical approval and informed consent of patients were obtained. An experienced sonographer estimated fetal weights by measuring BPD, HC, AC and FL using a scanner with Hadlock 3 weight estimation model. Actual birth weights were measured with a Crown weighing scale by a midwife. Data was analyzed with SPSS software version 17.0 while descriptive and inferential statistics were used to interpret results. Results were tested at error level set at p≤ 0.05.

RESULTS

Mean estimated and actual birth weights were 3378±40g and 3393±60g respectively. Difference between the two means was not significant. Eleven percent of fetuses were sonographically estimated to be microsomic while 14.5% were microsomic at birth; 12.1% were sonographically estimated to be macrosomic but 15.2% were macrosomic at birth. Most macrosomic fetuses were delivered through cesarean section(CS) and fetal weights increased with maternal age and parity.

CONCLUSION

Sonographically estimated fetal weight using Hadlock 3 weight estimation model without validation correlated positively with actual birth weight in a Nigerian population.

Evaluation of the accuracy of ultrasonography fetal weight estimation models; assessing regression formulae in a Turkish population

In this study, we aimed to evaluate the accuracy of fetal weight prediction, to investigate the validity of sonographic fetal anthropometric parameters in a Turkish population and to assess the most commonly used sonographic formulas for estimation of fetal birth weight. Our retrospective, cross-sectional study included 126 singleton deliveries between June 2010 and January 2011, at the Department of Obstetrics and Gynecology of the GATA Haydarpaşa Training Hospital. Ultrasonography measurement results were applied to nine different fetal weight estimation formulas. Mean error, mean absolute error, mean percentage error and mean absolute percentage error rates were calculated. Under- or overestimation rates and correlation coefficients were also calculated. Fetal biparietal diameter (BPD) and abdominal circumference (AC) were significantly correlated with the actual birth weight and the power analysis for both parameters was calculated as 81%. The highest correlation coefficients in our general population were those of the F1 (Hadlock 1) and F2 (Hadlock 2) models. The highest mean percentage error was detected on F8 (Merz 2) model. Fetal weight estimation modalities were observed to give the best results in a weight range of 3,000 and 3,500 g. Regression formulae used in our population, in general, tended to underestimate, however Hadlock 1 and 2 formulations provided the most accurate results. The Hadlock 1 formula estimated the closest to the actual birth weight in fetuses expected to be born under 3,000 g or over 3,500 g.