Breast-feeding and postpartum maternal weight trajectories

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.

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.

Large Irish university maternity hospital.

Women who delivered a baby weighing ≥500 g between November 2012 and March 2014.

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.

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.