Poster session I Clinical obstetrics, epidemiology, fetus, medical-surgical complications, neonatalogy, physiology/endocrinology, prematurity: Abstracts 87 - 236| Volume 208, ISSUE 1, SUPPLEMENT , S56-S57, January 01, 2013

100: Comparing estimated fetal weight by ultrasound and clinical assessment with actual birthweight


      To evaluate if there is a significant difference between two antepartum methods of estimating fetal weight immediately before birth and the actual birthweight.

      Study Design

      Fetal ultrasound was performed within 48 hours of delivery on term fetuses in women admitted to Sinai Hospital of Baltimore. Clinical estimates of fetal weight were obtained by attending and resident physicians. These estimates were then compared to the actual birthweight after delivery.


      We analyzed 47 of 51 recruited women. The median age was 28 years, median gestational age was 40 weeks, median BMI was 29.7 with 50% of patients between 26 and 32.8 kg/m2 and the mean birthweight was 3,451 ± 343 grams. There were 47% African American and 51% Caucasian women. The majority of patients were nuliparous (53%). The clinical fetal weight estimates by the attendings correlated better with the birthweight than did the resident's ((Pearson correlation 0.49 vs. 0.20). When attendings and residents estimated fetal weight on the same patient, only attendings' estimates were significant, r= 0.46 (p =0.01). Clinical estimates consistently overestimated birthweight at lower values and underestimated it at higher values (Figure). Multiple regression adjusting for maternal parity, age and BMI demonstrated that ultrasound correlated better with birthweight than clinical estimates (0.73). Attending but not resident estimates were significantly associated with birthweight in the model. Experience with ultrasound increased the correlation with birthweight (Pearson correlation 0.68 first half vs 0.79 second half). Various published equations for calculating fetal weight using different biometric parameters found that Hadlock ‘85 formula with BPD, HC, AC and FL was the best predictor (Table).
      Tabled 1Multivariate models for predicting birthweight
      Table thumbnail grr10


      Ultrasound was the best method to predict birthweight. Physician experience improves clinical prediction. No formula to predict fetal weight was better than the Hadlock ‘85 formula that includes cephalic, abdominal and femoral measurements.