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High Fetal Fraction on First Trimester Cell-Free DNA Aneuploidy Screening and Adverse Pregnancy Outcomes.

OBJECTIVE
 To test the hypothesis that high fetal fraction (FF) on first trimester cell-free deoxyribonucleic acid (cfDNA) aneuploidy screening is associated with adverse perinatal outcomes.


STUDY DESIGN
 This is a single-institution retrospective cohort study of women who underwent cfDNA screening at <14 weeks' gestation and delivered a singleton infant between July 2016 and June 2018. Women with abnormal results were excluded. Women with high FF (≥95th percentile) were compared with women with normal FF (5th-95th percentiles). Outcomes investigated were preterm birth, small for gestational age, and hypertensive disorders of pregnancy.


RESULTS
 A total of 2,033 women met inclusion criteria. The mean FF was 10.0%, and FF >16.5% was considered high (n = 102). Women with high FF had a greater chance of delivering a small for gestational age infant <fifth percentile, with an adjusted odds ratio of 2.4 (95% confidence interval: 1.1-4.8, p = 0.039). There was no significant association between high FF and either preterm birth or hypertensive disorders of pregnancy.


CONCLUSION
 Women with a high FF in the first trimester are at increased risk of delivering a small for gestational age infant <fifth percentile. Further investigation into the clinical implications of a high FF is warranted.