To investigate the clinical diagnostic value of ultrasonic testing of fetal nuchal translucency (NT) in the first trimester pregnancy (11-13^{+ 6} gestational weeks) combined with noninvasive prenatal test (NIPT) of fetal DNA in screening fetal disorders of sex development (DSD) of pregnant women with advanced age (≥35-year old).

According to the subsequence number on admission of pregnant women, 198 fetuses of singleton pregnancy with live birth of pregnant women with advanced age in the 901th Hospital of Joint Logistic Support Force of PLA from 2016 to 2018 were selected as research subjects by simple random sampling method of random number table. All pregnant women received ultrasonic testing of fetal NT in the first trimester pregnancy and NIPT of fetal DNA. Taking the diagnosis result made by multi-disciplinary team (MDT) experts according to the clinical manifestations and relevant examination results of neonates as " gold standard" for diagnosis of fetal DSD, the sensitivity, specificity and accuracy of ultrasonic testing of fetal NT in the first trimester pregnancy, NIPT of fetal DNA and the combination of these two methods in diagnosis of fetal DSD of pregnant women with advanced age were calculated, respectively. The procedures followed in this study were in line with the requirements of World Medical Association Declaration of Helsinki revised in 2013. The guardians of all subjects had informed consent and signed the informed consent form of clinical research.

Among the 198 fetuses, 28 cases were finally diagnosed as DSD after comprehensive evaluation by MDT. ① The sensitivity, specificity and accuracy of ultrasonic testing of fetal NT in the first trimester pregnancy in diagnosis of fetal DSD of pregnant women with advanced age were 89.3%, 71.2% and 73.7%, respectively. ② The sensitivity, specificity and accuracy of NIPT of fetal DNA in diagnosis of fetal DSD of pregnant women with advanced age were 85.7%, 78.2% and 79.3%, respectively. ③ The sensitivity, specificity and accuracy of ultrasonic testing of fetal NT in the first trimester pregnancy combined with NIPT of fetal DNA in diagnosis of fetal DSD of pregnant women with advanced age were 96.4%, 88.2% and 89.4%, respectively.

Fetal NT in the first trimester pregnancy combined with NIPT of fetal DNA has a certain value for diagnosis of fetal DSD of pregnant women with advanced age. As this study is just a single center study with small sample size, the value of fetal NT in the first trimester pregnancy combined with NIPT of fetal DNA in diagnosis of fetal DSD of pregnant women with advanced age still needs to be further confirmed by large-sample, multi-center and randomized controlled trials.