Changes in adipose tissue distribution during pregnancy in overweight and obese compared with normal weight women

Abstract

Objective: Differences in body fat distribution contribute to the metabolic abnormalities associated with overweight and obesity; however, such differences have not been adequately explored during pregnancy. Our aim was to compare longitudinal trends in maternal abdominal adipose tissue deposition during pregnancy in overweight/obese compared with normal weight women.

Study design: Pregnant women, classified as normal weight (body mass index (BMI) <25 kg m(-2); N=61) or overweight/obese (BMI 25 kg m(-2); N=57), were enrolled in a prospective cohort study starting in the first trimester. Maternal subcutaneous (smin) and preperitoneal (pmax) fat were measured by ultrasound at five time points starting between 6 and 10 weeks gestation. The abdominal fat index (AFI), an established marker of visceral adipose tissue, was calculated as the ratio of pmax to smin. The trajectories of smin, pmax, cumulative fat index (smin plus pmax) and the AFI across pregnancy were analyzed using mixed linear models.

Results: The rate of maternal weight gain during pregnancy was significantly lower for overweight/obese women compared with their non-overweight counterparts (P<0.05). Accordingly, the rate of change of pmax and smin differed significantly in normal weight compared with overweight/obese women (P=0.0003 and 0.01, respectively). The cumulative fat index did not change across gestation in normal weight women, whereas it decreased for overweight/obese women (P=0.0005). The log AFI increased across pregnancy in both strata, but significantly more rapidly for normal weight compared with overweight/obese women (P=0.06).

Conclusions: Adipose tissue is preferentially deposited in the more metabolically active visceral compartment as pregnancy progresses. However, this process differs in normal weight compared with overweight/obese women and may contribute to metabolic differences between these groups. Our study is a step toward a more refined description of obesity and its consequences during pregnancy.

Figure 1

Maternal weight gain. The cumulative maternal weight gain (effective maternal weight at each study visit minus prepregnancy weight) trajectories for normal weight (solid line) and overweight/obese women (dashed line). Regression lines were calculated using a mixed linear regression model. The difference in rate of change between BMI strata is statistically significant (P<0.05).

Figure 2

Maternal fat indices. Maternal abdominal fat thickness measures in normal weight (solid line; open circles) and overweight/obese (dashed line; crosses) women. Regression lines calculated using a mixed linear regression model are shown for normal weight women in blue and for overweight/obese women in red. P-values are provided for the significance of the difference in rate of change between BMI strata. (a) Preperitoneal fat thickness (pmax); P=0.0003. (b) Subcutaneous fat thickness (smin); P=0.01. (c) Cumulative fat index (smin+pmax); P=0.0005. (d) Logarithm of the AFI; P=0.06.