Obesity increases the risk of failure of noninvasive prenatal screening regardless of gestational age.

ABSTRACT

BACKGROUND: Noninvasive prenatal screening has become an increasingly prevalent choice for women who desire aneuploidy screening. Although the test characteristics are impressive, some women are at increased risk for noninvasive prenatal screen failure. The risk of test failure increases with maternal weight; thus, obese women may be at elevated risk for failure. This risk of failure may be mitigated by the addition of a paternal cheek swab and screening at a later gestational age. OBJECTIVE: The purpose of this study was to evaluate the association among obesity, gestational age, and paternal cheek swab in the prevention of screening failure. STUDY DESIGN: A retrospective cohort study was performed for women who were ≥35 years old at delivery who underwent screening at NorthShore University HealthSystem, Evanston, IL. Maternal weight, body mass index, gestational age, and a paternal cheek swab were evaluated in univariate and multivariable logistic regression analyses to assess the association with failed screening. RESULTS: Five hundred sixty-five women met inclusion criteria for our study. The mean body mass index was 25.9 ± 5.1 kg/m(2); 111 women (20%) were obese (body mass index, ≥30 kg/m(2)). Forty-four women (7.8%) had a failed screen. Obese women had a failure rate of 24.3% compared with 3.8% in nonobese women (P < .01). Gestational age was not associated with failure rate (mean ± standard deviation, 13 ± 3 weeks for both screen failure and nonfailure; P = .76). The addition of a paternal cheek swab reduced the failure rate from 10.2% in women with no swab to 3.8% in women with a swab (P < .01). In multivariable analysis, obesity and lack of a paternal cheek swab were independent predictors of screen failure (odds ratio, 9.75; 95% confidence interval, 4.85-19.61; P < .01; and odds ratio, 3.61; 95% confidence interval, 1.56-8.33; P < .01, respectively). CONCLUSION: The addition of a paternal cheek swab significantly improved noninvasive prenatal screen success rates in obese women. However, delaying testing to a later gestational age did not.