Background

Foetal weight is an important consideration when making decisions about intervention in labour. Although weight is estimated in the beginning of labour, the relevant decisions are made at the end of labour. It is not clear whether the estimation of weight at the beginning of labour is more accurate than the estimation at the end of labour.

Method

This prospective study included 214 pregnant women. Foetal weights were estimated at the time of admission, at full dilatation or before Cesarean section (CS) using Johnson’s formula and multiplying symphysio-fundal height by the abdominal girth measurement.

Results

The accuracy of estimation of weight by the Johnson formula (insert measuring tape) at the beginning of labour was similar to weight at the end of labour, but the weight obtained by multiplying the symphysio-fundal height by the abdominal girth (insert the measuring tape and holding it straight) at the beginning of labour was more accurate than the same process at the end of labour (p < 0.001). However, using the Johnson formula (holding the meter straight) at the end of labour was more accurate than it was at the beginning of labour (p = 0.02).

Conclusion

The accuracy of estimated weight varies depending on time, the method used, and the formula of measurement.