Impact of maternal body mass index (BMI) and the challenges of fetal echocardiography

Objectives
Fetal echocardiography is the gold standard modality to detect suspected congenital heart disease (CHD). Accurate diagnosis and subsequent prognosis is even more challenging in the presence of a raised maternal body mass index (BMI). This retrospective study aimed to gain insight into the prevalence of obesity within the cohort of patients referred for fetal echocardiography.

Study design/methods
Retrospective analysis of all pregnant patients referred to the Scottish National Fetal Cardiology Service between 2015 and 2021 due to a suspected fetal cardiac abnormality and examining the associated trends in maternal BMI and the Scottish Index of Multiple Deprivation (SIMD).

Results
BMI data were available for 962 (96.3%) of the 998 patients referred during the study period. Median BMI during the study period was 31. BMI range in the seven-year period was 16–63. There was no association between BMI group and year (P = 0.889). A median of 58% of patients referred were classified as overweight (BMI > 25 kg/m²), and only 37% were reported to have a BMI within normal limits. Referral BMI was relatively consistent in the seven years with no dramatic increase in the obese categories. Mean BMI in SIMD 5 (lowest level of deprivation), was significantly lower (P = 0.001), than in SIMD 1 (highest deprivation).

Conclusions
People of child bearing age should be aware the potential limitations that a raised BMI may have upon diagnostic/screening accuracy impacting subsequent ability to provide accurate fetal cardiac diagnoses and prognostic fetal cardiac imaging.