(118) Technical and maternal factors associated with fetal anatomic survey completion in higher BMI groups

To describe the proportion of completed fetal anatomic survey (FAS) at first attempt in patients with Body Mass Index (BMI) ≥40 kg/m², and to identify maternal and sonographic factors affecting FAS completion rates. 

Study Design: A retrospective single academic center study that included pregnant individuals with singleton gestation, presenting for a detailed FAS in 2019-2023 between 17 and 25 weeks’ gestation and are ³18yo with BMI³40 kg/m². Maternal and sonographic characteristics were compared between three BMI groups, 40-45.9, 46-49.9, and ≥50 kg/m², using adjusted and unadjusted analyses.

Results:

A total of 574 patients met inclusion criteria with 53% at BMI 40-45.9, 26% at BMI 46-49.9, and 21% at BMI ≥50. The groups did not differ in gestational age at detailed FAS, placental location, fetal position, machine type, duration of scan, time of day and sonographer experience (Table 1). Completion of the anatomy at first attempt for all BMI groups was less than 50%, with significant reduction as BMI category increased (p < 0.001 for all comparisons). The number of suboptimal anatomic systems did not differ between BMI groups, with the heart being the most common suboptimal system followed by spine and extremities (Table 1). The rate of fetal anomalies was 2%. After controlling for gestational age at anatomic survey, sonographer experience, placental location, fetal position, type of ultrasound machine, and time of day the scan was done, higher BMI remained significantly associated with lower rates of anatomy completion (aOR of 0.57, 95% CI 0.37-0.88 for BMI 45-49.9, and aOR of 0.34, 95% CI 0.20-0.56 for BMI≥50, both compared with BMI 40-44.9).

Conclusion:

Anatomy scan completion rates were low among individuals with BMI ≥40 kg/m2 and progressively decreased among BMI 45-49 and BMI ≥50. This could lead to potential delays in diagnosing fetal anomalies, necessitating alternative strategies such as advanced imaging technology, specialized training, pre-scan preparation and patient education, to ensure comprehensive prenatal care for individuals with higher BMIs.