ANTHROPOMETRIC EQUATIONS FOR STUDYING BODY-FAT IN PREGNANT-WOMEN

Anthropometric data from 200 pregnant women were used to estimate body fat at gestation weeks 14 and 37 and changes in body fat from week 14 to week 37 with four formulas from the literature. The resulting esti mates were evaluated against the estimation of fat by a four-compartme nt model that determined fat from weight, total body water, bone miner al mass, and body density. The estimates of fat by existing anthropome tric models were statistically different from those by the four-compar tment model in both early and late pregnancy. Most importantly, the ch ange in body fat estimated by the anthropometric models (all > 4 kg) w as considerably higher than that estimated by the four-compartment mod el (3.3 kg). Two new anthropometric equations were developed, both of which used the four-compartment model as the reference method. The equ ation for predicting change in fat mass from week 14 to 37 of pregnanc y was as follows: 0.77 (change in weight, kg) + 0.07 (change in thigh skinfold thickness, mm) - 6.13 (r(2) = 0.73). The equation for determi ning fat (kg) at term was as follows: 0.40 (weight at week 37, kg) + 0 .16 (biceps skinfold thickness at week 37, mm) + 0.15 (thigh skinfold thickness at week 37, mm) - 0.09 (wrist circumference at week 37, mm) + 0.10 (prepregnancy weight, kg) - 6.56 (r(2) = 0.89). Both equations were derived on a randomly selected half of the total sample and valid ated on the remaining half. Both equations were found to be valid for use in studying pregnant women with different prepregnancy body mass i ndexes, different gestational weight gains, different ethnicities, and different socioeconomic status.