Publication:

Comparison of three clinical and three ultrasonic equations in predicting fetal birth weight

Background Antenatal assessment of fetal weight is important part in the management decisions during labour, thereby improving perinatal outcome. There are a large number of clinical methods and ultrasonic formulae for predicting fetal birth weight (EBW) with varying degrees of accuracy. This study was an attempt to compare the accuracy of three clinical and three ultrasonic methods in Indian population. The method with highest accuracy can be used in high and low resource setting in a country like ours with diverse resource settings.

Methods This was a prospective non randomized cohort study done on 100 antenatal patients in PGIMER, Dr. RML Hospital; New Delhi from Nov 2011 to Jan 2013 EBW (Expected Birth Weight) was calculated applying the 6 formulae three clinical and three ultrasonic and statistical analysis done after delivery comparing with ABW (Actual Birth Weight).

Results Accuracy in all ABW within 10% of ABW was 94 % with Johnson's method, 92 %with Dares method and 62 % with obstetrical equation. It was 100% with Hadlock 2 equation, 96% with Shepherd's and 86% with Warsoff equation Sensitivity for IUGR i.e. wt <2.5 kg was low in clinical methods, highest was only 46.2% with Johnsons. In ultrasonic methods all the three equations had 100% sensitivity making ultrasound the preferred modality in diagnosing macrosomia.

Conclusions The major finding of this study is that clinical estimation of fetal weight is as accurate as ultrasonographic method of estimation within normal range of birth weight Ultrasonographic methods was statistically more accurate with smaller mean errors and more within 10% of actual birth weight. Johnson formula gave most accuracy in clinical methods Ultrasound should be used to confirm clinical methods if IUGR or Macrosomia is suspected. No single method should be used if EBW is a part of decision but two or more methods should be combined.