Skinfold caliper and ultrasound assessments of change in the distribution of subcutaneous fat during adolescent pregnancy

OBJECTIVE: This study compares skinfold caliper and sonographic measurements of the amount and distribution of subcutaneous adipose tissue teenagers gain during pregnancy to test three hypotheses: (1) skinfold caliper and sonographic measurements of subcutaneous adiposity are highly correlated in pregnancy; (2) the extent to which the skinfold caliper heads compact the tissues increases during gestation; and (3) skinfold caliper measurements yield a smaller estimate of the amount of subcutaneous adipose tissue gained during gestation than do sonographic measurements. METHODS: We studied 28 primiparous teenagers at 10.7 +/- 2.8 and 29.6 +/- 1.8 weeks gestation. At both study visits subcutaneous adipose tissue thickness was measured at six body sites, first by skinfold caliper and then by ultrasound. Taking the nearly compression-free sonographic measurements as the standard, we quantified the extent to which the skinfold caliper heads compacted the tissues at each measurement site by computing the percentage compression: (mean adipose tissue thickness by ultrasound - (0.5 x mean adipose tissue thickness by caliper)/mean adipose tissue thickness by ultrasound) x 100. Pearson correlations and paired t-tests were used to compare the skinfold caliper and sonographic measurements. RESULTS: Hypothesis 1 was supported; the skinfold caliper and sonographic measurements were highly correlated at both study visits. Hypothesis 2 was not supported; between study visits caliper-related tissue compression decreased at measurement sites on the trunk and remained the same at measurement sites on the extremities. Hypothesis 3 was also refuted; the skinfold caliper-derived estimate of the amount of subcutaneous adipose tissue gained on the trunk exceeded the corresponding sonographic determination. As anticipated, the skinfold caliper measurements indicated that adipose tissue was stored more rapidly on the trunk than the extremities, but the opposite pattern emerged when the sonographic measurement technique was used. CONCLUSIONS: The results of this study challenge the notion that pregnant women store adipose tissue preferentially on the trunk and suggest that pregnancy-related changes in the regional distribution of maternal body fat based on skinfold caliper measurements should be interpreted cautiously.