The Effects of Body Type on Maternal Fat Specialization During Pregnancy

It would be helpful to understand the anthropometric factors that influence fetal growth in order to maximize the number of infants born within the birthweight range that is least associated with morbidity and mortality (2,500-4,000 grams). Existing literature demonstrates that upper-body fat tends to fuel fetal growth, while lower body fat is stored to fuel lactation postpartum. However, there is little research into whether this phenomenon is consistent across all subgroups of women. This thesis analyzes data from a prospective cohort study that collected anthropometric data on 355 mother-infant pairs from the first prenatal visit to after delivery. These data support the hypothesis that the subgroup of women with large amounts of lower body fat and small amounts of upper-body fat is an exception to the general trend. This population was split between a Lower-Fat Only ‘Pear’ group and a ‘Non-Pear’ group according to a relative measure of fat distribution. A multiple regression analysis predicting fetal growth was run on these two groups, but BMI was replaced with a measure of lower body adiposity, thigh circumference, and a measure of upper-body adiposity, subscapular skinfold. In the ‘Pear’ subgroup, thigh circumference was significantly associated with fetal growth (b = 30.0g, p = 0.0389), while the subscapular skinfold was not (b = 2.8g, p = 0.8818). The opposite relationship was demonstrated in the ‘Non-Pear’ group. In the majority of the population, the subscapular skinfold was significantly related to fetal growth (b = 10.7g, p = 0.0009) while the thigh circumference was not (b = -1.6g, p = 0.7250). This adds nuance to the existing body of knowledge. It confirms that upper-body adiposity fuels fetal growth in the majority of women, but lower body fat fuels fetal group in the subgroup of women with large lower body fat stores and small upper-body fat stores.