GENDER-SPECIFIC 2ND-TRIMESTER BIOMETRY

OBJECTIVE: This study was designed to evaluate the significance of gen der differences for commonly used biometric parameters obtained ultras onographically from second-trimester euploid fetuses. STUDY DESIGN: Ge nder-specific linear regression equations were developed for gestation al age dependent and independent biometry from second-trimester ultras onographically normal singleton euploid fetuses by use of biparietal d iameters and femur and humerus lengths. Regression lines for male fetu ses were compared with those for females by determining overlap of 95% confidence intervals at specific points. RESULTS: A total of 288 male fetuses (mean gestational age 16.7 +/- 1.0 weeks) and 251 female fetu ses (mean gestational age 16.8 +/- 1.2 weeks) (not significant) were e valuated. Small statistically significant gender differences in fetal biometry were identified. The largest gender difference for gestationa l age-dependent parameters was a biparietal diameter difference of 1.1 5 mm at 21 weeks. The largest gender difference for gestational age-in dependent parameters was a femur length difference of 1.7 mm at a bipa rietal diameter of 50 mm. CONCLUSION: Statistically, but not clinicall y, significant gender differences of small magnitude exist for second- trimester fetal biometry, suggesting that gender-specific nomograms ma y be of limited value.