WEIGHT-GAIN DURING THE FIRST-YEAR OF LIFE IN RELATION TO MATERNAL-SMOKING AND BREAST-FEEDING IN NORWAY

Objective-To assess the weight gain during the first year of life in r elation to maternal smoking during pregnancy and the duration of breas tfeeding. Design-This was a one year cohort study. Setting-The city of Oslo, Norway. Participants-Altogether 3020 children born in Oslo in 1 992-93. Children were divided into three groups as follows: 2208 born to non-smoking mothers, 451 to mothers who were tight smokers (<10 cig arettes per day), and 261 to mothers who were heavy smokers (greater t han or equal to 10 cigarettes per day). Main results-The mean birth we ights were 3616 g, 3526 g, and 3382 g and 1 year body weights were 10 056 g (gain 6440 g per year), 10141g (6615 g), and 10158 g (6776 g) in children of non-smoking and light and heavy smoking mothers respectiv ely. Cox regression analysis showed that children of heavy smokers wer e 2.0 (95% confidence interval, 1.7, 2.3) times and children of light smokers 1.3 (1.2, 1.5) times more Likely to have stopped breast feedin g during their first year of life compared with children whose mothers were non-smokers. Linear regression analysis, adjusting for confounde rs, showed that weight gain was slower in breast fed children than in those who were not breast fed (-38 g (-50, -27) per month of breast fe eding). Compared with children of nonsmokers, the adjusted weight gain was 147 g (40, 255) per year greater in children of light smokers and 184g (44, 324) per year in children of heavy smokers. Conclusion-Chil dren catch up any losses in birth weight due to maternal smoking, but some of the catch up effect is caused by a shorter duration of breast feeding in children of smoking mothers.