Fetal biometry: does patient ethnicity matter?

Objective: To determine if fetal biometry varies according to race.

Methods: We performed a retrospective chart review of prenatal ultrasounds completed in our Perinatal Center from January 2009 to December 2010. Singleton pregnancies 17 to 22.9 weeks were included. Pregnancies complicated by IUGR, fetal anomalies, chronic maternal diseases, or dated by an ultrasound after the first trimester were excluded. Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and humerus length (HL) were compared between African Americans (AA), Caucasians, and Hispanics using ANOVA and Student t-test.

Results: Included were 1327 AA, 147 Caucasian, and 86 Hispanic subjects. The AC was significantly smaller in AA than Caucasians (p = 0.008). There was no difference between AA and Caucasians in BPD, HC, FL, or HL. There were no differences between Hispanics and either Caucasians or AA in any of the biometries evaluated.

Conclusions: A single fetal growth curve is not applicable across all ethnicities. AA fetuses have smaller AC then Caucasian fetuses from 17 to 22.9 weeks, which is typically the period when anatomic surveys are performed. Because AC contributes heavily to estimated fetal weight calculations, physicians may be over estimating growth restriction in AA patients. Ethnicity-specific fetal growth curves are indicated to limit unnecessary follow up.