Postpartum body composition changes in lactating and non-lactating primiparas

Abstract

The objective of this study is to evaluate the postpartum body composition changes in lactating versus non-lactating or formula-feeding primiparas during the first 12 wk. Twenty primiparous females (age range 17–35 y) who decided to nurse or formula feed their infant were studied. The non-lactating mothers (n = 6) were younger (21 versus 29 y) and had a lower prepregnancy weight (55 kg versus 63 kg) than the lactating mothers (n = 14). Body weight, height, waist and hip measurements, 3-d dietary and activity records, skin-fold thickness from triceps, suprailiac, midthigh, and midupper arm circumference, and total body composition were evaluated at three time periods (at delivery, at 6 wk, and at 12 wk postpartum). Total body composition for bone mineral, lean, and fat mass was measured by dual energy x-ray absorptiometry. At delivery and 6 wk postpartum, the weights and heights were similar between the two groups. By 12 wk postpartum, the formula-feeding group had a weight loss that was different from delivery, 66 ± 10 kg to 59 ± 8 kg, P < 0.03. There was no significant weight change in the lactating group during the study. The weight loss consisted of more lean mass than fat mass. The total body bone mineral content did not differ between the two groups during the study. Both groups had reduction in their waist size from delivery to 12 wk postpartum. But only the non-lactating mothers had reductions in their hip and midthigh measurements. There were no changes between the two groups in the skin-fold measurements. Lactating mothers had a higher total daily calories (1974 ± 318 versus 1464 ± 178 calories, P < 0.002) and fat intake (63 ± 14 versus 47 ± 9 g, P < 0.02) than the non-lactating mothers. The energy expenditure was similar between both groups. In conclusion, during the first 12 wk postpartum, non-lactating mothers who were younger and weighed less prepregnancy lost body weight and had more waist, hip, and midthigh size reductions compared to lactating mothers.

Introduction

Postpartum body composition changes, especially weight loss, are of concern for most women. During pregnancy, mothers experience an increase in fat and lean tissues in addition to the products of conception.1 The average weight gain for a term pregnancy is 10–12.5 kg.2 Following delivery, many mothers express the desire to return to their prepregnancy weight.3 The effect of lactation on postpartum body composition changes has been inconclusive, with some reports indicating that lactation promoted weight loss while others did not observe any changes.3, 4, 5, 6, 7, 8, 9, 10, 11, 12 The purpose of this study is to evaluate the postpartum body composition changes in lactating versus non-lactating or formula-feeding primiparas during the first 12 wk.