Fetal fractional limb volumes in pregnancies following bariatric surgery

Obesity rates have reached an epidemic level and bariatric surgery is the most effective method of sustainable weight loss. Pregnancy following bariatric surgery is associated with an increased prevalence of small babies. The objective of the study is to compare the fetal fat distribution, as assessed by fractional arm and thigh volume using three-dimensional ultrasonography, in pregnancies following maternal bariatric surgery with those without such history.

This is a prospective, longitudinal, observational study conducted in a Maternity Unit in the UK. The study included 189 pregnant women; 63 with previous bariatric surgery [27 restrictive (13 with gastric band, 14 with sleeve gastrectomy) and 36 malabsorptive procedures] and 126 with no previous surgery but similar maternal booking body mass index. Fetal arm and thigh volume were obtained at 30-33 and 35-37 weeks' gestation and fractional limb volumes were calculated using a commercially available software. Women underwent a 75 g, 2 h oral glucose tolerance test at 28-31 weeks of gestation.

Overall, adjusted fetal arm and thigh volume were smaller in the post-bariatric, compared to the no surgery, group and this was more marked in women who had undergone a previous sleeve gastrectomy (P < .001 and P = .002, respectively) or a malabsorptive procedure (P < .001 for both). There was a strong positive correlation between maternal fasting/post-prandial (2 h) glucose levels, at the time of the oral glucose tolerance test, and arm and thigh volume at both 30-33 and 35-37 weeks (P < .01 for all).

The study has demonstrated that in the third trimester of pregnancy, fetuses of women with previous bariatric surgery have smaller fractional limb volumes, therefore less soft tissue, compared to fetuses of women without such surgery and this may be related to the lower maternal glucose levels seen in the former pregnancies.