The Impact of Maternal BMI on Time of Transvaginal Cervical Imaging

Abstract

Introduction: Ultrasound is an integral part of obstetrical care and obesity has been shown to decrease the accuracy of ultrasound examination in high-risk pregnancy (Tsai et al, 2015). Obesity decreases the fidelity of ultrasound, as decreased visualization is seen with increasing depth of abdominal adipose tissue (Paladini, 2009). While maternal obesity has been shown to detrimentally impact anatomical ultrasound, the effects of obesity on the performance of transvaginal ultrasound are unclear. Our aim was to evaluate if obesity has an effect on the time required to obtain transvaginal cervical length. Methods: Retrospective chart review between January 2016-January 2022 identified patients with cervical shortening (<2.5 cm) at the time of mid-trimester anatomical ultrasound scans. Scans were performed at the Maternal Fetal Medicine Department at Promedica Toledo Hospital between 16- and 24-weeks gestation. Patient BMI was recorded at the time of ultrasound and divided into obese (BMI ≥ 30 kg/m²) and non-obese (BMI ≤ 30 kg/m²) categories. Time to complete transvaginal ultrasound imaging was recorded in both patient populations and compared. Results: 216 patients met study criteria. Out of the 216, 89 (41%) were obese and 127 (59%) were non-obese. Average BMI of all participants was 29.2 ± 7.4 kg/m². Average time spent on ultrasound for patients with BMI <30 was 13:36 ± 01:28 and for BMI >30 15:34 ± 01:48 (p=0.46). There was no statistical difference between obese and non-obese patients and transvaginal scanning time > 10 minutes (OR 1.24, 95% CI 0.719-2.13, p=0.44) Discussion: Our results suggest that the time to obtain cervical length measurements via transvaginal ultrasounds is similar between obese and non-obese patients. Time necessary to perform endovaginal ultrasonography of the cervix does not appear to be affected by maternal BMI. Since length of time necessary to complete transvaginal cervical length measurement does not appear to be affected by maternal BMI, our results suggest that additional scheduling time does not need to be allocated for obese patients. Other investigators have shown that early incorporation of transvaginal assessment of fetal anatomy in obese women improved the rate of survey completion and demonstrated earlier completion of the fetal anatomic evaluation (Toscano et al, 2021). This study encourages the further use of transvaginal ultrasound in obese, obstetrical patients.