[Influencing factors of resampling failure for non-invasive prenatal testing and its influence on pregnancy outcomes]

Objective: To evaluate the factors influencing test failure after resampling in non-invasive prenatal testing (NIPT) and to explore its impact on pregnancy outcomes. Methods: The information of pregnant women who failed to undergo NIPT for the first time and resampled for testing in Beijing Obstetrics and Gynecology Hospital, Capital Medical University from January 2018 to January 2022 were collected and retrospectively analyzed. According to the results of resampled NIPT, the pregnant women were divided into the failure group (170 cases) and the success group(485 cases), and the general clinical data and pregnancy outcomes of the two groups were compared. Results: (1) A total of 88 928 pregnant women underwent NIPT in Beijing Obstetrics and Gynecology Hospital during the study period, of which 1 299 (1.461%, 1 299/88 928) failed in the first NIPT. Among the 1 299 pregnant women who failed in the first NIPT, 720 were resampled for testing. Finally, 655 pregnant women who met the inclusion criteria and had complete clinical information and perinatal outcomes were collected. The success rate of resampling was 74.0% (485/655). Compared with the success group, the pregnant women in the failure group had a later gestational age at resampling, a higher pre-pregnancy body mass index (BMI) and a higher fetal fraction, and the differences were statistically significant (all P<0.001). (2) Among the 485 pregnant women in the success group, 130 cases (26.8%, 130/485) were detected with chromosome aneuploidy. Among the 170 pregnant women in the failure group, 8 cases had abnormal amniocentesis, 2 cases had abnormal maternal serum screening of aneuploidy in the second trimester, 3 cases had abnormal ultrasound anomaly removal, and 157 cases had no abnormality. (3) The incidence of fetal or neonatal malformation in the failure group was significantly higher than that in the success group [11.2% (19/170) vs 5.8% (28/485), P=0.019], but after adjusting for age and pre-pregnancy BMI, fetal or neonatal malformation was not associated with the success of resampling (RR=0.675, 95%CI: 0.346-1.319; P=0.250). The incidences of gestational diabetes mellitus and hypertensive disorders in pregnancy in the failure group were significantly higher than those in the success group (all P<0.05), but after adjusting for age and pre-pregnancy BMI, only the incidence of gestational diabetes mellitus in the failure group was higher (RR=0.630, 95%CI: 0.426-0.932; P=0.021). Conclusions: For pregnant women who failed the initial NIPT, the success of the resampling test is associated with pre-pregnancy BMI and the gestational week at the time of resampling. Those who failed the resampling test are more likely to develop gestational diabetes mellitus. When providing genetic counseling for pregnant women who failed the initial NIPT, it is important to consider the successful rate of resampling testing. The risk of chromosomal abnormalities should be comprehensively considered to develop further screening strategies.