The Effects of Birth Interval on Infant Mortality

Some of the arguments for the benefits of family planning focus on the health of women and children in the developing  world.

Dr Shea O Rutstein has done several studies into the importance of extending birth intervals in developing countries. In the papers cited, estimates are made for survival rates of infants and young children.  The finding demonstrate that if birth intervals were extended to 24 months, the deaths of almost 2 million children under 5 would have been averted.

The education of women and the availability of adequate birth control methods has benefits for both the women and their children. Rutstein’s initial study was conducted in 2005 and published in the International Journal of Gynecology and Obstetrics

Effects of preceding birth intervals on neonatal, infant and under-five years mortality and nutritional status in developing countries: evidence from the demographic and health surveys. S.O. Rutstein

Since at least 1923, the deleterious effect of short interbirth and/or interpregnancy intervals for maternal and child health has been investigated. The effect of short intervals has been demonstrated many times to be one of the most important factors affecting the mortality of infants and young children. Little research has been done, however, on determining the optimal birth interval rather than establishing the relationship between birth intervals and mortality. It is the purpose of this paper to determine whether there is an optimal interval for the mortality of children under age 5 years and, if so, to establish the optimal spacing window in order to guide mothers. As such, this paper reports on the analysis of the effects of birth spacing on infant and child mortality, and on nutritional status, controlling for the effects of potentially confounding variables.

The study used 17 countries surveyed in the Retrospective survey data of the Demographic and Health Surveys (DHS) program and used NCHS/CDC/WHO international reference standards for height for age, weight for age, and weight for height. Attempts were made to control for nutrition status, breastfeeding duration, and other factors.

Previous recommendations to women have been to avoid having birth sooner than 24 months apart. While the excess risk of mortality is highest for very short birth intervals (less than 18 months), there are relatively few children born with such intervals (16%). Combining both the increased risk of birth earlier than 36 months with the great number of birth with such intervals results substantial declines in mortality by avoiding intervals of 24 to 35 months. For the year 2003, if women in developing countries (excluding China) would not have had any births at intervals less than 24 months; they could have averted almost 2 million deaths in that year to children under age 5 years. An additional almost 1 million deaths in that year would have been averted if mothers had spaced at least 36 months between births. The deaths that would have been averted account for about 35% of all deaths to children less than 5 years of age in 2003

For the surveys where significant results have been established, children face a double whammy to a healthy life from short preceding birth intervals: the risk of dying and the risk of being malnourished.

In 2008, Rutstein expanded the data set to include 52 DHS surveys conducted from 2000 through 2005, and confirmed the results.

The population attributable risk (PAR) for under-five mortality for avoiding conceptions at less than 24 months after a birth is 0.134. In other words, if all women would wait at least 24 months to conceive again, under-five deaths would fall by 13 percent. The effect of waiting 36 months to conceive again would avoid 25 percent of under-five deaths. The impact of avoiding these high risk intervals (less than 36 months) would be a total of 1,836,000 deaths avoided annually in less developed countries.

For neonatal mortality, the adjusted risk ratios indicate that risk of dying decreases with increasing birth to pregnancy interval lengths up to 36 months and rises for conceptions after 48 or more months. This rise was indicated in the previous study for birth intervals of five and more years but the increase was not statistically significant. The larger data set now confirms that this rise is statistically significant.

For post-neonatal mortality, the decrease of the risk of dying with increasing interval is again similar to those of early neonatal, neonatal and infant mortality. However, there is no
corresponding increase with duration of interval for children conceived after the reference group (i.e. after an interval of 48 or more months).

For the risk of dying between ages one and four years, also known as child mortality, the adjusted risk ratios indicate that the longer the birth interval, the lower the risk, even for  intervals of 48 or more months.

The risk of being chronically malnourished (stunted and/or underweight) decreases with increasing time between the preceding birth and the conception of the child under study. In
contrast with the effects on mortality, there is no levelling or increase in the risk of being stunted or underweight for long birth intervals.

Studies have also shown maternal deaths increase with decreasing birth interval, and are  decreased by contraceptive use.  Organizations such as Safe Motherhood and the Bill and Melinda Gates Foundation are tackling these problems head on with campaigns focusing on family planning through education and access to contraception and safe abortions.

Organizations such as the Catholic Church, Focus on the Family, and some Islamic groups fight these initiatives to the detriment of mothers and their children, as well as to the men who lose their wives and children.  This is not protecting men, women, children, or families. This is sacrificing all in the name of religion.

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