Information was collected on maternal age, gestational age, medical history (including IVF-ET, RSA and fetal malformations) and prenatal aneuploidy screening results (including primary screening and NIPT). Prior to the logistic regression analysis, four groups were created: under 20 years, 20–34 years, 35–39 years and 40 years and older, with 20–34 years being the unexposed group and the remaining groups being the exposed group. Similarly, cases with unremarkable medical history were included in the unexposed group and cases with a history of IVF-ET, RSA and fetal malformations were included in the exposed group. The incidence of each type of fetal aneuploidy under different maternal risk factors was counted based on karyotype reports of fetal or aborted tissue.
In this study, the risk levels for prenatal aneuploidy screening and NIPT were determined according to relevant guidelines and expert consensus in mainland China. In short, all pregnant women should undergo primary screening and NIPT is not necessary for all. The decision on the need for prenatal diagnosis is also based on these results. It is important to emphasize that the doctor only provides guidance and advice throughout the pregnancy and that the pregnant woman has complete independence of choice. For primary screening, any of the following is considered high risk: NT < 2.5–3.0 mm in early pregnancy, abnormal fetal growth parameters throughout pregnancy and a Down’s screening result above 1/270 of the cut-off (biochemical markers and algorithms are being introduced to estimate risk, including AFP, total hCG, unconjugated estriol and free beta-hCG). For NIPT, free fetal DNA fragments purified from maternal peripheral plasma are sequenced using DNA sequencing technology, and the results are subjected to data processing and bioinformatic analysis. The NIPT is considered high risk if the detection risk index exceeds a threshold of 3, otherwise it is considered low risk. Based on the results of primary screening and NIPT, karyotypes were counted under different screening results.
In this study, the risk levels for prenatal aneuploidy screening and NIPT were determined according to relevant guidelines and expert consensus in mainland China. In short, all pregnant women should undergo primary screening and NIPT is not necessary for all. The decision on the need for prenatal diagnosis is also based on these results. It is important to emphasize that the doctor only provides guidance and advice throughout the pregnancy and that the pregnant woman has complete independence of choice. For primary screening, any of the following is considered high risk: NT < 2.5–3.0 mm in early pregnancy, abnormal fetal growth parameters throughout pregnancy and a Down’s screening result above 1/270 of the cut-off (biochemical markers and algorithms are being introduced to estimate risk, including AFP, total hCG, unconjugated estriol and free beta-hCG). For NIPT, free fetal DNA fragments purified from maternal peripheral plasma are sequenced using DNA sequencing technology, and the results are subjected to data processing and bioinformatic analysis. The NIPT is considered high risk if the detection risk index exceeds a threshold of 3, otherwise it is considered low risk. Based on the results of primary screening and NIPT, karyotypes were counted under different screening results.
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