AbstractObjectiveThe objectives of the study are to assess the accuracy of noninvasive prenatal testing (NIPT) for sex chromosome aneuploidies (SCAs) and to investigate patient decision‐making in clinical practice.Study designThis is a retrospective cohort study review of positive NIPT results for SCAs from January 2013 to September 2017.ResultsOf the 136 positive NIPT results for SCAs, 73 (53.7%) were positive for 45,X, 62 (45.6%) were a sex chromosome trisomy, and 1 was a sex chromosome tetrasomy. Of the 134 viable pregnancies, 46 (34.3%) elected to pursue prenatal diagnosis. Fewer women underwent invasive prenatal testing when counseled regarding a positive NIPT for monosomy X in the presence of suggestive ultrasound findings (4/23; 17.4%) compared with those who had a positive NIPT result without ultrasound findings (24/46, 52.2%). Abnormal karyotypes consistent with the NIPT result were confirmed in 30/64 (46.9%). Even in the context of ultrasound abnormalities, there was not 100% concordance.ConclusionsThe majority (88/134; 65.7%) of patients in our cohort declined prenatal diagnosis even in the presence of associated ultrasound findings. Comprehensive pretest and posttest counseling is recommended and should address the importance of confirmatory testing and benefits of early diagnosis. Practice guidelines are needed to address provider responsibilities about postnatal testing.