A review of sonographic estimate of fetal weight: vagaries of accuracy.

PURPOSE: To determine the factors that might influence the accuracy of sonographic estimated fetal weight. STUDY DESIGN: A PubMed search (Jan 1975 to Jan 2003) of articles published in the English language was carried out and the inclusion criterion was that estimates were within 10% of birth weight. A Chi-square test for trend was used and odds ratio (OR) with 95% confidence intervals (CI) was calculated. RESULTS: Over 28 years, 175 articles were identified but only 54 (31%) met the inclusion criterion. Overall 62% (8895/14 384) of the predictions were within 10% of the actual weight. The accuracy was significantly different in articles where <7 vs. >7 days were allowed to lapse between examination and delivery (OR 2.17, 95% CI 1.93, 2.45); where examinations were done by registered diagnostic medical sonographers (RDMS; 65%) versus physicians (59%) or residents (57%; p < 0.0001); in term vs. preterm patients (OR 1.97, 95% CI 1.67, 2.13); and in studies with >1000 vs. <1000 cohorts (OR 1.62; 95% CI 1.51, 1.74). CONCLUSIONS: If feasible the sonographic examination should be done by RDMS and within a week of delivery.