226: Cell-free DNA fetal fraction and pregnancy outcome

Abstract

Fetal cell-free DNA from maternal plasma during pregnancy is a fairly new technology that is increasingly being used to screen for aneuploidy. Limited reports show that low and high fetal fraction percentages may be associated with increased risks of adverse pregnancy outcomes. The purpose of this study is to determine if high or low fetal fraction percentages are associated with adverse pregnancy outcomes to include hypertensive disorders, low birth weight, and preterm delivery. A retrospective chart review was performed evaluating pregnancy outcomes for 200 patients who underwent cell-free fetal DNA screening from January 2016 until October 2017. The estimated gestational age at delivery, birth weight, and presence or absence of hypertensive disorders was recorded and their association with their fetal fraction percent was evaluated. The mean fetal fraction percent was 11.9%. Average gestational age at collection was 17 1/7 weeks. A distinct bimodal distribution at the time of collection was noted (less versus greater than 20 weeks). Fetal fraction percent was directly related to gestational age at collection and inversely related to patient’s weight and body mass index. Patients with low fetal fraction percents had more than twice the rates of hypertensive disorders compared to patients with higher fetal fraction percents (34.6% versus 14.2%, P< .05). Low fetal fractions drawn prior to 20 weeks gestational age had more than 3 times the rate of preterm delivery (31% versus 9%, p< .05). For patients undergoing screening after 20 weeks gestational age, a high fetal fraction percent was associated with lower birth weight (mean birth weight 3056g versus 3457g, p< .05) High and low fetal fraction percentages are markers for adverse pregnancy outcomes such as hypertensive disorders, low birth weight, and preterm delivery. Patients with such values may warrant closer monitoring during their pregnancy with additional appointments, blood pressure assessments, ultrasound assessments, and further education regarding the signs and symptoms of preeclampsia and preterm labor.View Large Image Figure ViewerDownload Hi-res image Download (PPT)