Child and maternal mortality and morbidity are examined in relation to the interval between pregnancies. Most data available pertain to child mortality. Very little reliable information links child morbidity or maternal health detriments to short birth spacing. The evidence on child mortality suggests that very short intervals (conceptions less than six months after a birth) are detrimental to survival of the second child, but these results must be viewed in light of the methodological difficulties of studies of this subject. Policy implications of the data are perhaps less clear than is sometimes assumed.
PIP: The health effects of birth spacing remain relatively obscure despite frequent exhortation to space pregnancies in order to improve maternal and child health. Most studies have not controlled for very important confounding factors. More needs to be known about the relationship of birth interval to child health apart from maternal age and parity. It is important to control for socioeconomic effects and prior child deaths because these factors are so closely associated with differentials in health risks. For example, the raw data of Fedrick and Adelstein's work suggested a birth interval effect on survival, with higher risks at the longest intervals; correction for age and socioeconomic class completely eliminated an effect except in the very shortest interval. We do not yet know which months of postneonatal mortality are most affected by short birth interval, nor understand whether the effects are more likely due to prematurity and/or low birth weight, or to nutritional status and child care at the commencement of weaning. More needs to be known about the mechanism of excess risk for siblings born into families with a prior early child death. Also in many societies where birth interval effects on mortality have been demonstrated, the distribution of births is already relatively favorable. A very small percentage of children are subject to the risks of the shortest intervals, and a great majority of births already occur with greater than 24-month spacing. Perhaps where traditional lactation practices help avoid the worst hazards of short intervals, emphasis on delaying the 1st birth and/or making available the means for women to limit their fertility may have as much impact on health as birth spacing alone. Birth intervals may be most measurable in situations where general infant and child mortality patterns are already high. Finally, we do not know how to measure the health effects of high fertility or short intervals on mothers or their effects on healthy women of low parity and their children.