Longitudinal Changes in the Relationship Between Body Mass Index and Percent Body Fat in Pregnancy

Obstet Gynecol. 1997 Mar;89(3):377-82. doi: 10.1016/S0029-7844(96)00517-0.


Objective: To determine the longitudinal relationship between body mass index (BMI) and percent body fat in women before and during pregnancy.

Methods: Twenty-seven healthy, nonobese women were evaluated before conception, in early gestation (12-17 weeks), and in late gestation (33-36 weeks). Height and weight were measured and BMI was calculated. Percent body fat was estimated using hydrodensitometry with correction for residual lung volume.

Results: The correlation between BMI and percent body fat before conception was r = 0.693 (P < .005); in early gestation it was r = 0.723 (P < .005) and in late gestation r = 0.633 (P < .005). The mean pregravid BMI was 21.54 and the 95% predictive confidence interval (CI) for percent body fat was 18.2, 26.5%. For the mean BMI of 22.26 in early gestation, the predictive 95% CI for percent body fat was 20.0, 29.0%. In late gestation, the mean BMI was 26.04 with a predictive 95% CI for percent body fat 22.5, 30.8%.

Conclusion: In nonobese women the correlation between BMI and percent body fat remains significant during pregnancy, although the 95% CI for predicting percent body fat from the mean BMI ranges widely.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adipose Tissue*
  • Adult
  • Body Mass Index*
  • Confidence Intervals
  • Female
  • Humans
  • Longitudinal Studies
  • Pregnancy