Prenatal diagnosis and pregnancy determination of sex chromosome aneuploidy screened by non-invasive prenatal testing from 52,453 unselected singleton pregnancies: a retrospective analysis of 4-year experience

Abstract

Objective To estimate the positive predictive value (PPV) of fetal sex chromosome aneuploidy (SCA) screened in non-selective population and explore the rate of pregnancy termination and ultrasound findings for fetal SCA and the factors influencing parents’ decisions in South China. Methods This is a large-scale retrospective cohort of positive SCA screened from unselected singleton pregnancies by non-invasive prenatal testing (NIPT) from a single prenatal center of a tertiary hospital, from January 2016 to November 2019. Clinical information, indications, diagnostic results, ultrasound findings, pregnancy determinations, and follow-up were reviewed and analyzed. Results 248 cases of SCA positive were screened out of 52453, giving a positive detection rate of 0.47%. The majority of indications (42.7%) were low-risk pregnancies. After genetic counseling, 43 pregnancies (17.3%) declined to prenatal diagnosis, the rest of 205 cases (82.7%) conducted with amniocentesis to detect fetal chromosome, of which 95 were confirmed as true positive of SCA with PPV of 46.3% (95/205). The SCA consisted of 68 sex chromosomal trisomies (26 cases of 47,XXY, 20 cases of 47,XXX and 22 cases of 47,XYY), 17 cases of monosomy X (45,X), three cases of 48,XXYY, three cases of mosaicisms (45,X/46,XX), four cases with sex chromosomal deletions, included two cases of 46,X,del(Y)(q11.21), one case of 46,X,del(X)(p11) and one case of 46,X,i(X)(q10). Of the 95 cases confirmed as true positive SCA, 50 cases (52.6%)chose to terminate the pregnancy (82.6%, 64.3%, 17.6% and 33.3% for 45,X, 47,XXY, 47,XXX and 47,XYY, respectively), 45 cases (47.4%) elected to continue the pregnancy. Ninety-three pregnant were also continued pregnancy after the exclusion of SCA. Conclusions NIPT, as a first-tier routine method for screening autosomal aneuploidies, also could play an important role in screening SCA. Low-risk pregnant women are the main indication for the detection of SCA as NIPT test provides to non-selective population. The trend of overall termination rates of SCA-affected pregnancies is decreased. For 47,XXX and 47,XYY with mild phenotype, couples would like to continue the pregnancy. But for 45,X and 47,XXY, parents apt to terminate pregnancy no matter ultrasound abnormalities were found or not. pregnancy determinations are affected by types of SCA, sonographic findings, maternal age, and presence of infertility.