The Role of Early Gestation Ultrasound in the Assessment of Fetal Anatomy in Maternal Obesity

Abstract

Objectives: The 2012 Eunice Kennedy Shriver National Institute of Child Health fetal imaging consensus suggested that fetal anatomy ultrasound in obese pregnancies be performed at 20 to 22 weeks, with follow-up in 2 to 4 weeks if anatomy is incomplete. It was postulated that imaging in early gestation may improve visualization, although no prospective trials had been done to date.

Methods: We performed a prospective longitudinal blinded trial comparing an early gestation ultrasound (13 + 0 to 15 + 6 weeks) with the traditional second-trimester ultrasound for completion of the fetal anatomy survey in obese patients. Inclusion criteria included singleton gestation, body mass index (BMI) more than 30, less than 16 + 0 weeks' gestation, and no karyotype abnormality; exclusion criteria included age younger than 18 years, more than 16 weeks' gestation at time of consent, and BMI less than 30. Participants received a transvaginal and/or transabdominal sonogram for fetal anatomic survey at 13 + 0 to 15 + 6 weeks' gestation (US1). Images from US1 were blinded to physicians and sonographers performing subsequent examinations. All participants underwent the traditional transabdominal sonogram at 18 to 24 weeks (US2). If US2 failed to complete the anatomic survey, a repeat transabdominal sonogram (2-US2) was performed 2 to 4 weeks later.

Results: A total of 152 pregnancies met the criteria. Anatomy completion rate was 57.2% for US1 and 62.5% for US2, which was not statistically significant, even when stratified by BMI. Excluding the philtrum, the US1 performed better than US2 for class III obesity (65.5% versus 45.5% [P = .035]). Combination of US1 + US2 yielded a higher completion rate than US2 + 2-US2 (94.1% versus 83.6% [P = .0023]).

Conclusions: In the setting of maternal obesity, the addition of an ultrasound in early gestation may be of highest benefit for patients with class III obesity (BMI > 40 kg/m² ).

Keywords: morphology; obesity; ultrasound.