Johnson-Toshach’s method compared with ultrasound to determine fetal weight in term pregnant women attended at Cajamarca Regional Hospital

Abstract

Objective: To compare Johnson-Toshach’s method and ultrasonography in estimating fetal weight in term pregnant women. Design: Descriptive, comparative, prospective, longitudinal study. Institution: Hospital Regional de Cajamarca, Cajamarca, Peru. Participants: Term pregnant women. Methods: Uterine height was measured and fetal weight was estimated by Johnson-Toshach’s formula in 236 pregnant women 37-41 weeks. Subsequently, an obstetric ultrasound was performed in the same women to determine the fetal weight according Hadlock´s 2 formula. Delivery was expected within 48 hours; then the weight of the newborn was obtained. Statistical analysis was done using SPSS 19 statistical package, student t and McNemar tests with p<0.05 significance. Main outcome measures: Fetal weight. Results: Fetal weight estimated by Johnson-Toshach’s method was more accurate than that calculated by ultrasonography with relative error 6.5% versus 8.6% (p=0.001). Ultrasound sensitivity was significantly better than Johnson-Toshach’s method for estimating fetal macrosomia (75% versus 62.5%, p=0.013). Johnson-Toshach’s method was significantly more sensitive than ultrasound to detect fetuses with normal weight (98% versus 89.3%, p=0.016). Furthermore ultrasonography showed better sensitivity than Johnson-Toshach’s method to detect low birth weight fetuses (57.8% versus 51.2%), but this difference was not significant (p=0.238). Conclusions: Fetal weight estimated by Johnson-Toshach’s method was more accurate than ultrasonography in pregnant women between 37 and 41 weeks gestation who carried fetuses between 2 501- 3 999 g.