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Longitudinal changes in the relationship between body mass index and percent body fat in pregnancy
C A Lindsay1, L Huston, S B Amini
1Department of Reproductive Biology, Case Western Reserve University, Metro Health Medical Center, Cleveland, Ohio, USA.
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.