ACTA FAC MED NAISS 2018;35(4):320-329

Original article

UDC: 618.29(55)

DOI: 10.2478/afmnai-2018-0034

Error Analysis for Determination of Accuracy of Johnson’s Formula, Dare’s Formula and Mother's Opinion for the Estimation of Birth Weight: Results of an Iranian Cross-Sectional Study

Somayeh Alirezaei¹, Elham Azmoude², Asma Ghaderi³

¹Ph.D. Student in Reproductive Health, Student Research Committee, Faculty of Nursing and Midwifery, Mashhad University of Medical Sciences, Mashhad, Iran
²Department of Midwifery, Faculty of Nursing and Midwifery, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran
³Student Research Committee, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran

summary


Accurate fetal weight estimation is important for the management of birth. According to the existing literature, none of the clinical techniques is superior to any other. This study aimed to compare error analysis for the determination of the accuracy of Johnson’s formula, Dare’s formula and mother's opinion for the estimation of birth weight.
A cross-sectional study involving 147 full-term, cephalic, singleton pregnancies, was performed. The mother’s opinion was recorded and Johnson’s and Dare’s formulas were used to calculate the fetal weight. Accuracy was determined by percentage error, absolute percentage error, and proportion of estimates within 10% of actual birth-weight. Statistical analysis was done using the RM ANOVA, Friedman and Cochran. P < 0.05 was considered significant.
The birth weight was correctly estimated to 34.7%, 58.5%, 66% of the cases using the mother’s estimate, Dare’s and Johnson’s formulas. Respectively the proportion of the mother's estimate and Dare’s formula was significantly lower than that of Johnson’s formula for all birth weights. No significant difference was observed in all the measures of accuracy for the low birth-weight range. The mean error of Johnson's formula in both normal weight and macrosomal groups was less than those obtained by the Dare's formula and mother's opinion.
The Johnson’s formula is more accurate in actual birth weight estimation than the Dare ’s one and mother's opinion. In the normal weight range, Johnson’s formula is more accurate of the two, while in the macrocosmic group, Dare’s formula appears to be more accurate.

Key words: fetal weight, birth weight, Iran