Breast-feeding and postpartum maternal weight trajectories.

OBJECTIVE: We examined whether breast-feeding, and in particular exclusive breast-feeding, was associated with maternal weight and body composition changes at 4 months postpartum independently of other maternal variables. DESIGN: Prospective longitudinal study. Women were recruited in the first trimester after an ultrasound examination confirmed an ongoing singleton pregnancy. Weight and body composition were measured using advanced bio-electrical impedance analysis at the first antenatal visit and 4 months postpartum. Detailed questionnaires were completed on breast-feeding, socio-economic status, diet and exercise in addition to routine clinical and sociodemographic details. SETTING: Large Irish university maternity hospital. SUBJECTS: Women who delivered a baby weighing ≥500 g between November 2012 and March 2014. RESULTS: At the postpartum visit, the mean weight was 70·9 (sd 14·2) kg (n 470) and the mean BMI was 25·9 (sd 5·0) kg/m2. 'Any breast-feeding' was reported by 65·1 % of women (n 306). Irish nativity (OR=0·085, P<0·001), current smoking (OR=0·385, P=0·01), relative income poverty (OR=0·421, P=0·04) and deprivation (OR=0·458, P=0·02) were negatively associated with exclusive breast-feeding. At 4 months postpartum there was no difference in maternal weight change between women who exclusively breast-fed and those who formula-fed (+2·0 v. +1·1 kg, P=0·13). Women who exclusively breast-fed had a greater increase in percentage body fat at 4 months postpartum compared with women who formula-fed (+1·0 v. -0·03 %, P=0·02), even though their dietary quality was better. Exclusive breast-feeding was not associated with postpartum maternal weight or body fat percentage change after adjusting for other maternal variables. CONCLUSIONS: There are many reasons why breast-feeding should be strongly promoted but we found no evidence to support postpartum weight management as an advantage of breast-feeding.