The Impact of Pre-Pregnancy Maternal Obesity on Nuchal Translucency Measurement at Time of First- Trimester Screening: A Single Center Retrospective Analysis

Objective: To evaluate the impact of pre-pregnancy maternal obesity on Nuchal Translucency (NT) measurement during a first trimester screen ultrasonographic examination. Methods: Using the Magee-Women's Hospital Ultrasound Database, a retrospective cohort study of women with singleton pregnancies undergoing successful NT screening from January 2008 to October 2013 was performed. Body Mass Index (BMI) was calculated from available pre-pregnancy height and weight data. The relationship among obesity, gravidity, parity, diabetes status, maternal age, ethnicity, pre-pregnancy weight and NT measurement was analyzed via multivariable linear regression. BMI categories and NT thresholds for consideration of invasive fetal testing for aneuploidy were examined via χ2 test and t-test, when appropriate. A P-value <0.05 was considered statistically significant. Results: Among 24, 862 women with singleton pregnancies, 7,408 (29.8%) cases were identified. After adjustment for confounders, increasing pre-pregnancy maternal BMI was significantly associated with a larger NT measurement (P<0.0001). Those with a BMI ≥40kg/² had a significant association with a NT measurement of 3.5mm or greater (P=0.028). Mean NT measurements between BMI <30kg/² and BMI ≥ 30kg/² were not statistically significant but trended toward an increased NT in the BMI ≥ 30kg/² cohort (1.62mm vs. 1.67mm: p=0.31). Conclusion: Pre-pregnancy BMI greater than or equal to 40kg/² is significantly associated with a NT measurement of 3.5mm or greater at time of first trimester screen.