Ultrasound measurement learning of fetal sex during the first trimester: does the experience matter?

摘要

Objective: To determine the probability of correctly diagnosing fetal sex during the first trimester by ultrasound according to crown–rump length (CRL) and previous ultrasound experience. Methods: A cohort study was performed from March 2012 to April 2013. The 2,314 first trimester pregnancy ultrasounds were examined. Eight sonographers, according to previous ultrasound experience, were divided into two groups: senior and junior. For fetal sex estimation, the method of a sagittal section and the relation between the angle formed by the genital tubercle and spinal column was used. Results: In 1,986 cases, fetal sex was diagnosed, with a success rate of 90.1%. A directly proportional relationship between the rate of success in fetal sex diagnosis and CRL ( P <0.001) was described. The rate of success in male fetuses was significantly higher than in female fetuses (94.6% vs 86.3%, respectively), P <0.001. In the senior sonographers group, the rate of overall success was 89.2% vs 90.5% in the junior group, the difference not being significant. The experience of sonographers did not reach statistical significance (95% confidence interval: 0.871–1.031; P =0.213). Conclusion: The prediction of fetal sex over 65 mm of CRL in both sexes is approximately 95% and from 76 mm onward is 99%. Both CRL and fetal sex influence the rate of success; however, the experience of a sonographer has not proven to be an influential factor. These results could be explained because the technique for diagnosing sex during the first trimester is very simple to learn.