Pregnancy-related changes in body fat

Objective: To determine patterns of subcutaneous body fat change from preconception through 6 weeks postpartum, and factors that modify them. Study design: A prospective study of 557 healthy women enrolled prior to pregnancy. Main outcome measure: Body weight and skinfold thickness at the thigh, triceps, and subscapula, preconception, in each trimester, and 6 weeks postpartum, along with other variables. Results: Subcutaneous body fat stores remained stable (P>0.13) during the first 6 weeks after conception, and increased from 6 to 35 weeks by 1.5 mm at the triceps, 4.2 mm at the subscapular, and 7.3 mm (P<0.01) at the thigh areas. Body fat changes correlated poorly with weight changes, reflecting differences in the time course for the changes. They differed by preconceptional body mass index (BMI), parity, and infant gender (P<0.05). Women with the highest BMIs tended to gain less subcutaneous fat early, primiparous women gained more at thigh (P=0.01) and subscapular (P=0.027), and women carrying males had higher gains at the thigh (P=0.032) and subscapular sites (P=0.058) than other women. Breastfeeding status did not affect postpartum body fat changes, but women who breastfed exclusively had significantly lower skinfold thicknesses than non-exclusive breastfeeders from preconception through 6 weeks postpartum (P=0.041). Conclusion: Subcutaneous body fat is stored and utilized at different sites at specific times during and after pregnancy. The pattern and amount of change varies depending on characteristics of women and their pregnancies.