Biometric measurements in fetuses of different race and gender.

Sonographic fetal biometric measurements on 6082 low-risk patients were compared in the second and third trimesters of pregnancy with respect to fetal race and gender. Ultrasonic measurements were obtained from fetuses of women participating in the Routine Antenatal Diagnostic Imaging with Ultrasound Study (RADIUS), who underwent both an early sonographic evaluation between 15 and 22 weeks' gestation and a later scan between 31 and 35 weeks' gestation. In the 16-21-week scans, male fetuses had significantly larger biparietal diameter measurements compared to female fetuses (estimated difference 0.852 mm, 95% CI 0.737-0.967). There was only minimal difference in biparietal diameter between Black and White fetuses. Femur length was similar in both female and male fetuses, but longer in Black compared to White fetuses (estimated difference 0.808 mm, 95% CI 0.539-1.078). During the 31-35-week scans, male fetuses continued to have larger biparietal diameter measurements compared to female fetuses (estimated difference 1.22 mm, 95% CI 1.04-1.40), and femur lengths were persistently longer in Black compared to White fetuses (estimated difference 0.563 mm, 95% CI 0.234-0.893). Further investigation is necessary to evaluate the effect of these slight differences in morphometric fetal measurements between races and genders, so that we can determine how best to use them for optimizing prenatal care. Copyright 1993 International Society of Ultrasound in Obstetrics and Gynecology