孕妇外周血胎儿游离DNA无创产前检测失败原因的初步分析

Preliminary analysis of the cause for the failure of non-invasive prenatal testing using cell-free fetal DNA derived from peripheral maternal blood

目的探讨孕妇外周血胎儿游离DNA无创产前筛查（non—invasive prenatal testing，NIPT）检测失败的原因。方法对31832例NIPT的检测结果进行回顾，分析孕妇的临床数据，并对其妊娠结局进行随访。结果在31832例NIPT检测中，首次检测失败200例。199例孕妇选择了再次采血检测，171例（85．9％）获得了有效的NIPT结果，28例（14．1％）仍无有效结果，NIPT检测最终失败率为0．088％。在28例检测失败的孕妇中，11例（39．2％）是由于总游离DNA含量过高，无法进行测序，17例（60．7％）经测序发现胎儿游离DNA含量〈4％。在171例再次检测获得有效结果的孕妇中，NIPT结果提示21三体高风险4例、18三体高风险1例、13三体高风险1例。经羊水细胞染色体核型分析，共发现3例47，XN，＋21，1例46，XN，rob（21；21），1例47，XN，＋18。1例13三体高风险为假阳性。在28例NIPT检测失败的孕妇中，14例正常分娩，新生儿无异常表现。9例在中晚孕期选择引产，其中因母体因素引产4例，因胎儿因素引产5例。4例孕妇发生了妊娠并发症。1例随访情况良好，尚未分娩。4例失访。在11例因总游离DNA含量过高而检测失败的孕妇中，6例在中晚孕期选择引产，比例为54．5％，显著高于胎儿游离DNA含量过低的孕妇（17．6％）。结论不应将单次采血NIPT检测无效认定为胎儿染色体非整倍体高风险。若再次采血检测仍然失败，则应加强对孕妇的遗传咨询和围产期保健。

Objective To explore the cause of failure of non-invasive prenatal testing （NIPT） using cell-free fetal DNA from peripheral maternal blood. Methods A total of 31 832 cases of NIPT were retrospectively analyzed. The clinical data of pregnant women were analyzed and the outcome of pregnancy was followed up. Results Among the 31 832 cases, 200 patients have failed for the first NIPT test. Second test has succeeded in 171 （85.9%） of 199 cases, while 28 cases （14.1~） still yielded no effective results. This gave rise for a total failure rate of 0. 088%. Of the 28 cases, 11 （39.2%） were due to high content of total free DNA and could not be sequenced, 17 （60.7%） were found to have the fetal DNA content of less than 4%. Among the 171 cases which have obtained a valid result, NIPT showed that there were 4 patients with high risk of trisomy 21, 18 cases with high risk of 18 trisomy and 1 case with high risk of 13 trisomy. Karyotyping analysis of the amniocytic chromosomes has identified 3 cases with 47, XN, ＋ 21, 1 case with 46,XN,rob（21;21）, 1 case with 47,XN,＋18, while the 13 trisomy case was found to be false positive. For the 28 cases with failed NIPT retest, 14 had normal delivery, with no anomaly noticed in the neonates. Nine patients had opted for artificial abortion during middle or late pregnancy due to maternal factors （4 cases） or fetal factors （5 cases）. Four patients developed complications of pregnancy. One case was in good condition upon follow-up. Four cases were lost during follow-up. Of the 11 pregnant women who had failed the NIPT test due to high content of total free DNA, 6 （54. 5%） had opted for artificial abortion during midterm pregnancy, which was significantly higher than that of pregnant women with low free DNA content （17.6%）. Coneluslon Failure of NIPT testing should attract attention from researchers. Failure of single NIPT test should not be regarded as a high risk signal for fetal chromosomal aneuploidies. For those where the test has failed again, genetic counseling and strengthened perinatal care should be provided for the pregnant women.