The impact of maternal obesity on second trimester ultrasound examination times.

Abstract

Background: Maternal obesity has become one of the most significant problems in obstetric practice1. Attenuation and refraction of the ultrasound beam by adipose tissue results in a loss of image resolution and suboptimal visualisation2. The studies primary objective evaluated the impact of maternal obesity on the time taken to complete the second trimester ultrasound examination. Secondary objectives compared two measures of obesity, maternal body mass index (BMI) and maternal adipose thickness (MAT) with examination time according to sonographer experience and gestational age. Summary of work: A retrospective cohort analysis was performed of consecutive low risk singleton second trimester morphology ultrasound examinations over a three-month period. Examination time was calculated and compared to BMI, and the measured MAT. The impact of gestational age and sonographer experience on overall examination time was evaluated. Thirty-five sonographers performed the ultrasound examinations with a range of experience stratified in years as well as basic and advanced skill level. Summary of results: There were 352 examinations included for data analysis, with 168 pregnant women (47.7%) in the overweight or obese BMI categories. The mean examination time for all examinations was 45.9 mins (SD=37.5). No significant difference in mean examination time was demonstrated between the BMI categories (overweight BMI - 46.3 mins (SD=40.3), Obese I BMI - 51.2 mins (SD=31.8), Obese II - 42.5 mins (SD=29.0), Obese III - 43.3 mins (SD=9.9), p = 0.275). There was a weak correlation between examination time and MAT (r = 0.22, p = <0.001). The advanced sonographer cohort displayed a weak correlation (r = 0.28, p = 0.001) with examination time compared to MAT. Discussion and conclusions: Maternal obesity does not extend the low risk second trimester ultrasound examination. No correlation was demonstrated between examination time and fetal gestational age. The advanced sonographer group moderated examination times depending on maternal size.