Birth spacing and infant and early childhood mortality in a high fertility area of Bangladesh: age-dependent and interactive effects.

To examine the effects of birth spacing on early childhood mortality, 3729 singleton births in 1983-84 were followed for 3 years in rural Bangladesh. Logistic regression analyses were used to assess whether the survival of older siblings modifies the effect of preceding birth intervals and to see if the effects of preceding and succeeding birth intervals are inter-related, controlling for the effects of sex of the child, mother's age and household economic status. With the exception of the neonatal period, birth spacing effects were highly significant. A preceding birth interval of < 15 months was associated with a greater mortality risk in the post-neonatal period for children with an older sibling who survived infancy. However, a short preceding birth interval did not adversely affect post-neonatal mortality if the older sibling died in infancy. Neonatal and post-neonatal deaths were higher if older siblings had died in respective age intervals. A pregnancy interval of < 12 months after childbirth raised the risk of death at ages 1-2 years considerably if the child was born after a short birth interval (< 15 months). The results suggest that the high mortality risks of closely spaced children are due to sibling competition for parental resources.