Fetal sex determination by high resolution ultrasound in early pregnancy

Objective: Fetal sex determination by ultrasound, and its medical and ethical implications, has been predominantly discussed in mid and late gestation. The development of high resolution ultrasound equipment has provided the possibility of detailed visualization of the fetus in early pregnancy. The present prospective study investigates the feasibility and accuracy of fetal sex determination by transabdominal ultrasound in early pregnancy. Methods: Sonographic determination of fetal sex was attempted prospectively prior to genetic amniocentesis in 173 fetuses from 11 to 16 weeks of gestation. The result of ultrasound examination was compared with the karyotype obtained from amniotic fluid cells. Results: Sonographic sex determination was feasible in 80.3% of cases, and all these determinations proved to be correct. There was no difference in the identification rate between male (n=87) and female (n=86) sex. Fetal sex determination was also feasible and correct in all four sets of twins and in the one set of quadruplets. Conclusion: Fetal sex assignment in the late first and early second trimester can be useful in pregnancies at risk for severe sex-linked diseases, in fetal disorders involving the genitalia, and in the individual identification of multiple fetuses. Prenatal sex assignment in early pregnancy implicates also far-reaching ethical problems because of the potential risk of sex-selected abortion.