Fetal biometry: a comparison of family physicians and radiologists

While performance and reading of obstetric sonograms is a skill widely taught in family practice residency programs, no prior studies have compared ultrasound performance and interpretation in residency programs with that of hospital radiologists. This study compares results of fetal biometry for gestational age determination performed sequentially by faculty-supervised residents and radiologists.

This retrospective chart review selected cases from among all gravidas who had ultrasound performed in a family practice residency clinic between January 1992 and April 1999. Biometry was performed by residents under the supervision of faculty preceptors who had ultrasound training and experience. A patient was included if (1) results of both a family practice ultrasound and a radiologist-read hospital ultrasound were present in the chart, (2) both studies were done before 36 weeks gestation, and (3) the family practice examination preceded the hospital study. The difference in expected date of confinement between resident and radiologist ultrasound was calculated, and this difference was evaluated for statistical significance by a paired sample t test.

Ninety-two ultrasound pairs were assessed, a sample size that provided .90 power to detect a gestational age estimate difference of 3 days between family practice and radiologist interpretations. The normally distributed observed mean difference in gestational age estimates was only 1.5 days.

This study found no difference in gestational age assessment performed by closely supervised family practice residents in comparison to radiologists.