Introduction: Fetal birth weightis an important predictor of neonatal problems and an useful indicator of intrauterine environment indirectly reflecting the health of mother. Accurate estimation of fetal weight is vital in the management of labor and delivery. Aims and Objectives: Tostudy the assessment of fetal weight in term pregnancy by Johnson’s formula and comparison with actual birth weight of baby. Methodology: This was a Prospective Study carried out at medical college and hospital from January 2009 to October 2010 in the department of obstetrics and gynecology. Two hundred women at term were studied. The fetal weight was estimated at the time of admission by using Johnson’s formula. Thestatistical analysis done by SPSS 17 version. Result: The mean of baby’s weight at birth was 2643 gms with 331.14 standard deviation on either side. Minimum value of Jonson’s formula was below that of minimum 2000 actual weight of babies. Determined weight by Johnson’s formula had mean error of 273 gms over that of actual weight. Johnson’s formula had 11.3% mean error of birth weight. The Johnson’s formula significantly differed from the actual birth weight (P<.000). In Johnson’s formula error of more than 200gms had it in 68.5% babies. Johnson’s formula can determine 55.5% accurately birth weight with 15% error. In 74% babies birth weight was overestimated by Johnson formula; of them 56.5% babies weight was estimated above 200 gms. Birth weight was underestimated in 26% babies and 12% babies had weight determined less than 200gms of actual weight. Johnson’s formula can predict accurately in 14% with 100gms difference. Conclusion: From our study it can be concluded that Johnson’s Formula is least accurate in predicting fetal birth weight, so other methods like USG and Symphysio fundal methods should be used to calculate the fetal birth weight.

Keywords: Fetal Birth Weight; Johnson’s Formula; Symphysiofundal Height.