Influencing factors and pregnancy outcomes of unsuccessful cell-free DNA testing in maternal perinatal blood / 中华围产医学杂志

ABSTRACT

Objective:To explore the possible factors leading to failure of cell-free DNA (cfDNA) testing in maternal peripheral blood and analyze the pregnancy outcomes of this group of pregnant women.Methods:This retrospective study involved 5 195 women who underwent cfDNA testing in Peking University Third Hospital from April 2017 to April 2019. Based on the first cfDNA testing results, clinical characteristics of the pregnant women with successful (success group, n=5 107) and failed (failure group, n=88) cfDNA testing were compared using Mann-Whitney U test and Chi-square test. Multivariate logistic regression was used to analyze the risk factors of cfDNA testing failure and the effect of body mass index (BMI) on the success rate, and evaluate the feasibility of re-sampling and the factors affecting the unsuccessful testing of a second sample. Results:The failure rate of first cfDNA testing was 1.7% (88/5 195). Successful cfDNA testing was achieved in 74 (87.1%, 74/85) of 85 re-sampling cases, while results of the other 11 cases (12.9%, 11/85) remained invalid. Thus, the final failure rate was 0.2% (11/5 195). Multivariate logistic regression revealed that increased maternal age ( OR=1.086, 95% CI 1.023-1.152, P=0.006), BMI ( OR=1.083, 95% CI 1.021-1.149, P=0.008) and twin pregnancies ( OR=3.093, 95% CI 1.715-5.577, P<0.001) were the risk factors of cfDNA testing failure, while increased cell-free fetal DNA (cffDNA) concentration ( OR=0.758, 95% CI 0.720-0.761, P<0.001) was a protective factor. The overweight (BMI 25-29.9 kg/m 2) and obese (BMI≥30 kg/m 2) women were 3.626 ( OR=3.626, 95% CI 2.298-5.724, P<0.001) and 4.064 ( OR=4.064, 95% CI 1.779-9.284, P=0.001) times more likely to have failed cfDNA testing than those with normal weight (BMI 18.5-24.9 kg/m 2), respectively. The success rate of re-testing decreased as the maternal BMI increased, regardless of the time interval between the two samplings ( OR=0.840, 95% CI 0.699-1.245, P=0.065). Seven out of the 74 cases with successful results in re-testing were at high risk, including one 45,X and one 47,XXY, confirmed by karyotyping amniocentesis. Among the 11 pregnant women with a failed testing after second sampling, eight underwent prenatal diagnosis with normal fetal chromosome karyotypes, and the other three cases without prenatal diagnosis all gave birth to neonates with normal phenotype. There was no statistical difference in the incidence of pregnancy loss between the failure and success group [9.1% (8/88) vs 2.5% (128/5 107), P=0.090]. Conclusions:Pregnant women with advanced age and higher BMI, lower cffDNA fraction and twin pregnancies are more likely to fail in cfDNA testing. For obese women, blood sampling can be postponed to a larger gestational age to reduce the failure rate. For pregnant women with failed testing in first sampling, a re-sampling is recommended, moreover, prenatal diagnosis is necessary for those had high-risk results or failed in re-testing.