This study was performed to determine the rates of breastfeeding among singletons, twins and triplets in Japan, and identify factors associated with the decision to breastfeed or bottle-feed. We analyzed a database of medical check-up of infants aged 3 to 6 months between April 2001 and July 2004 in Nishinomiya City in Japan. This medical check-up is given to almost 100% of infants in Japan and the data of 15,262 infants were analyzed. Among these, 14,963 (98.0%) were singletons, 290 (1.9%) were twins and 9 (0.1%) were triplets. Exclusive breast-feeding was chosen by 6680 (43.8%) mothers, mixed-feeding by 4645 (30.4%) mothers, and bottle-feeding with formula milk only by 3900 (25.6%) mothers. The rate of exclusive breastfeeding among twins or triplets was significantly lower than among singleton babies: 4.1% among twins or triplets, and 44.7% among singletons. Moreover, twins and triplets were independently associated with a higher rate of bottle-feeding: the odds ratio indicated that mothers who had twins or triplets were 2.44 times more likely to choose bottle-feeding with formula milk only than those who had singletons. Sucking ability at birth was associated with a higher rate of bottle-feeding: the odds ratio indicated that mothers who had infants with poor sucking ability at birth were 1.56 times more likely to choose bottle-feeding as those who had infants with normal sucking ability.

This study was performed to determine the rates of breastfeeding among singletons, twins and triplets in Japan, and identify factors associated with the decision to breastfeed or bottle-feed. We analyzed a database of medical check-up of infants aged 3 to 6 months between April 2001 and July 2004 in Nishinomiya City in Japan. This medical check-up is given to almost 100% of infants in Japan and the data of 15,262 infants were analyzed. Among these, 14,963 (98.0%) were singletons, 290 (1.9%) were twins and 9 (0.1%) were triplets. Exclusive breast-feeding was chosen by 6680 (43.8%) mothers, mixed-feeding by 4645 (30.4%) mothers, and bottle-feeding with formula milk only by 3900 (25.6%) mothers. The rate of exclusive breastfeeding among twins or triplets was significantly lower than among singleton babies: 4.1% among twins or triplets, and 44.7% among singletons. Moreover, twins and triplets were independently associated with a higher rate of bottle-feeding: the odds ratio indicated that mothers who had twins or triplets were 2.44 times more likely to choose bottle-feeding with formula milk only than those who had singletons. Sucking ability at birth was associated with a higher rate of bottle-feeding: the odds ratio indicated that mothers who had infants with poor sucking ability at birth were 1.56 times more likely to choose bottle-feeding as those who had infants with normal sucking ability.

This study was performed using population-based data to analyze whether motor development in early life is different between singletons and twins in Japan. For better comparison and investigation, we divided the 2 groups into a group with a birthweight of 2.5 kg or greater (subgroup A) and a group with a birthweight of less than 2.5 kg (subgroup B), respectively. We analyzed the database of medical check-ups for children aged 3 years between April 2001 and July 2004. They received medical checkups at 4 months, 1.5, and 3 years of age. Children who were suspected of having neurological abnormality or disability were referred to specialists and excluded from the database. The data of 14,132 children were analyzed. Among these, 13,040 (92.3%) children were singletons in subgroup A, 75 (0.5%) were twins in subgroup A, 866 (6.1%) were singletons in subgroup B and 151 (1.1%) were twins in subgroup B. The mean age at achieving milestones was slower in twins of subgroup A for each developmental outcome than singletons of subgroup A, and the difference between twins and singletons was significant after adjustment for rolling over. On the contrary, after adjusting for a confounding factor (gestational age), singletons of subgroup B attained motor development facilitating walking independently slower than twins of subgroup B. There were different tendencies in the results regarding the motor development of subjects of subgroup A and that of subjects of subgroup B.