Advertisement

The effect of maternal body mass index on fetal ultrasound image quality

Published:April 24, 2021DOI:https://doi.org/10.1016/j.ajog.2021.04.248

      Objective

      More than 60% of women are overweight or obese in the United States, with obesity the most common clinical risk factor in obstetrical practice.
      World Health Organization
      Obesity and overweight.
      ,
      • Maxwell C.
      • Glanc P.
      Imaging and obesity: a perspective during pregnancy.
      Although increasing maternal body mass index (BMI) is thought to be associated with lower ultrasound image quality,
      • Maxwell C.
      • Glanc P.
      Imaging and obesity: a perspective during pregnancy.
      • Paladini D.
      Sonography in obese and overweight pregnant women: clinical, medicolegal and technical issues.
      • Dashe J.S.
      • McIntire D.D.
      • Twickler D.M.
      Maternal obesity limits the ultrasound evaluation of fetal anatomy.
      no large-scale studies have quantified the effect in real-world settings. We investigated the effect of BMI on image quality of standard fetal views at the time of the routine midtrimester ultrasound.

      Study Design

      Retrospective analysis of ultrasound images, using a large real-world dataset, prospectively acquired at the John Radcliffe Hospital in Oxford, United Kingdom, during routine anomaly screening (18–23 weeks’ gestation) on 5 different ultrasound machines by 20 qualified sonographers. After institutional review board approval, all images were fully anonymized. Detailed, objective quality scoring
      • Yaqub M.
      • Kelly B.
      • Stobart H.
      • Napolitano R.
      • Noble J.A.
      • Papageorghiou A.T.
      Quality-improvement program for ultrasound-based fetal anatomy screening using large-scale clinical audit.
      of each ultrasound image (without knowledge of maternal BMI) was undertaken by a team of 12 independent sonographers. We assessed 6 standard views: the transventricular and transcerebellar head views, abdominal circumference, femur length, sagittal spine, and coronal view of the lips. For each image, a quality score was generated.
      • Yaqub M.
      • Kelly B.
      • Stobart H.
      • Napolitano R.
      • Noble J.A.
      • Papageorghiou A.T.
      Quality-improvement program for ultrasound-based fetal anatomy screening using large-scale clinical audit.
      Nonparametric testing was used to assess the association between BMI category (<25, 25–30, 30–35, and ≥35 kg/m2) and quality on all images (pooled analysis, significance level set at P<.05). We also assessed the impact of BMI on individual image criteria for each view.

      Results

      We assessed 26,954 ultrasound images from 3251 women, with 1788 (55%), 843 (26%), 383 (12%), and 237 (7%) in the 4 BMI groups, respectively. There was a decrease in image quality with increasing maternal BMI for all views (Figure) (Kruskal Wallis test, P<.05). Some clinical criteria were more affected by BMI than others (Figure): for instance, the visibility of the cavum septi pellucidi in the transventricular and transcerebellar views and visibility of the umbilical vein in the abdominal circumference view decreased most with higher BMI category. Magnification criteria were not significantly affected by BMI, probably because magnification, a geometric criterion, does not directly relate to image appearance and is under the control of the sonologist.
      Figure thumbnail gr1
      FigureComparison between BMI category and the mean quality score for all images
      Comparison between BMI category (blue, <25 kg/m2; orange, 25–29.9 kg/m2; gray, 30–34.9 kg/m2; yellow, ≥35 kg/m2) and the mean quality score for all images (main panel, P<.05). The mean quality score for each criterion in each of the 6 standard views are shown in panels (A) head in the TV plane, (B) sagittal view of the spine, (C) abdominal circumference (D) head in the TC plane (E) femur length, and (F) coronal view of the lips.
      BMI, body mass index; TC, transcerebellar; TV, transventricular.
      Yaqub. Effect of maternal body mass index on fetal ultrasound image quality. Am J Obstet Gynecol 2021.

      Conclusion

      We assessed ultrasound images of standard fetal views taken during routine midtrimester ultrasound examinations, scored these images objectively, and assessed image quality by maternal BMI. Using a large “real-world” image dataset acquired by a large number of sonographers on multiple ultrasound machines, we were able to show a consistent and substantial effect: the higher the maternal BMI category, the less likely fetal images were to satisfy quality criteria, and some criteria were more affected than others (Figure). These raise important clinical concerns: as an example, the poor visibility of the cavum septi pellucidi with increasing BMI is important, because visualization is an important marker of normal brain development and closely associated with the formation of the corpus callosum. In addition, the finding that head, abdomen, and femur views are affected by BMI category is of relevance for fetal biometry, because measurements are performed on these images. Whether measurements are less robust according to maternal BMI remains to be evaluated by examining the reproducibility of measurements in women with normal and high BMI. The largest consecutive differences were between image scores for BMI categories 30 to <35 and at least 35 kg/m2, suggesting that fetal image quality degrades most for maternal BMI of ≥35 kg/m2. This adds an important limitation to imaging, information which should be shared with women attending routine fetal anatomy scans.

      Acknowledgments

      We thank Intelligent Ultrasound Limited who developed the manual audit tool. The support of the 12 expert reviewers who performed the audit is gratefully acknowledged.

      Supplementary Data

      References

        • World Health Organization
        Obesity and overweight.
        (Available at:)
        • Maxwell C.
        • Glanc P.
        Imaging and obesity: a perspective during pregnancy.
        AJR Am J Roentgenol. 2011; 196: 311-319
        • Paladini D.
        Sonography in obese and overweight pregnant women: clinical, medicolegal and technical issues.
        Ultrasound Obstet Gynecol. 2009; 33: 720-729
        • Dashe J.S.
        • McIntire D.D.
        • Twickler D.M.
        Maternal obesity limits the ultrasound evaluation of fetal anatomy.
        J Ultrasound Med. 2009; 28: 1025-1030
        • Yaqub M.
        • Kelly B.
        • Stobart H.
        • Napolitano R.
        • Noble J.A.
        • Papageorghiou A.T.
        Quality-improvement program for ultrasound-based fetal anatomy screening using large-scale clinical audit.
        Ultrasound Obstet Gynecol. 2019; 54: 239-245