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

Abstract

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.

PIP: Logistic models were established to estimate the likelihood of child survival (neonatal, postneonatal, and one to two years mortality) in Bangladesh based on short birth intervals and controlling for socioeconomic and demographic factors. Data were obtained from the Teknaf Demographic Surveillance System Project of the International Center for Diarrheal Disease Research for 4184 singleton births in 1983-84. Variables include birth spacing, survival status of older sibling, maternal age, number of older surviving siblings, sex of the index child, and household socioeconomic status. 89% had a preceding sibling born in the previous five years. The average birth interval was 30 months. About 43% of neonatal and 25% of postneonatal mortality occurred among infants with preceding birth intervals of under 15 months. There were no significant differences between birth intervals of 15-23 months and over 23 months, so these groups were merged into over 15 months. Neonatal and postneonatal mortality was higher among infants with a birth interval of under 15 months and whose older sibling survived than among those with long birth intervals and surviving older siblings. About 10% of index children surviving to 12 months had a 12-month birth interval between the index child and the preceding child. When index children's intervals were under 15 months, mortality was 200/1000. Neonatal mortality risks were 38% higher among infants with a birth interval of under 15 weeks, but the effects were statistically insignificant. The mortality risk among index children was 1.9 times higher with an older sibling dying in the neonatal period, 1.4 times higher with mothers aged under 34 years, 2.4 times higher with birth intervals of under 15 months and a surviving older sibling, and 2.1 times higher with birth intervals over 15 months and postneonatal mortality of an older sibling. The infant mortality risk at one to two years of age was 1.9 times higher among index children with birth intervals of under 12 months. Interaction terms between preceding birth and subsequent pregnancy increased the odds of infant mortality by 6.1 times. Mothers aged under 20 years had lower infant mortality. Household assets were unrelated to neonatal mortality and weakly related to postneonatal mortality.