OC80: First‐trimester determination of fetal gender by ultrasound

Abstract

Objective: To determine the feasibility of correctly identifying fetal gender from 11 to 13 weeks of gestation. Methods: Fetal gender assessment by ultrasound was prospectively carried out in 425 singleton pregnancies at 11–13 weeks of gestation (confirmed by crown-rump length or biparietal diameter) immediately before chorionic villus sampling for karyo-typing. A total of 425 women underwent a detailed assessment of fetal anatomy at 11–13 weeks of gestation by means of transabdominal and transvaginal sonography. Fetal gender was identified in transverse and sagital planes, and was confirmed by chorionic villus sampling. Results: The accuracy of sex determination increased with gestation from 91.7% at 11 weeks, to 97.2% at 12 weeks and 100% at 13 weeks. Male fetus were wrongly assigned as female in 5.5% of cases in 11 weeks, 2.4% at 12 weeks and 0% at 13 weeks. The accuracy of correctly identifying fetal gender increased with gestational age. Conclusion: Whilst the accuracy of sonographic determination of fetal gender at 11–13 weeks is good, our decision on invasive testing for sex-linked conditions should be undertaken only after 12 weeks of gestation.