Obesity and Cell Free DNA Testing [24R

Abstract

INTRODUCTION: Cell free fetal DNA is first detected in maternal serum at seven weeks gestation and the quantity increases during pregnancy. Non-invasive prenatal testing (NIPT) can be used as a screening test to aid in prenatal diagnosis of fetal aneuploidy. Recommendations for use are limited to women at “high risk.” There are no current guidelines for use in special populations including obese women, “low risk” women, or smokers. In obese women, the amount of maternal cfDNA is greater than in non-obese women. We hypothesize that obese women will have greater rates of “no result” than lean women. METHODS: A retrospective review was performed evaluating all pregnant women at our institution who had NIPT drawn From 1/1/11-1/1/15 (n=805). Women with BMI between 25.0-29.9 at initial prenatal visit were excluded. Categorical variables were compared using chi square or Fisher's exact test, continuous variables were assessed using a student t test. RESULTS: A total of 473 women met inclusion criteria (277 obese, 196 normal weight). A larger proportion of obese women had “no result” than lean women but this was not statistically significant (3.2% vs 1.5%, p=0.24). The mean BMI in those with “no result” was 36.2+/-13.0. One obese woman had a female result on NIPT and male genitalia on ultrasound and confirmed at birth to be 46, XY. CONCLUSION: There was a trend toward more “no result” in obese vs lean women. A larger study is needed to further elucidate the differences in performance of NIPT for lean vs obese women.