• Editors' Summary
• Credits

1. Exploring the New Evidence
• Findings from the DHS Study
• Findings from the CLAP Study
• Why Are Longer Intervals Better?
2. Actual Versus Preferred Birth Intervals
3. Contraception for Spacing Births
4. Who Has Shorter Intervals?
5. How Programs Can Help Couples Space Births

• Figures
• Tables
• Side-bars
• Bibliography

• Why are longer intervals better?
• Spacing: A matter of choice
• How to measure intervals
• Women want longer intervals
• Demand for spacing is high
• Infant deaths shorten intervals
• Traditional practices can help
• Health programs can spread the message

• POPLINE
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Published by the Population Information Program, Center for Communication Programs, The Johns Hopkins University Bloomberg School of Public Health, 111 Market Place, Suite 310, Baltimore, Maryland 21202, USA.

Several biological and behavioral mechanisms are often cited to explain how short birth intervals affect infant and maternal mortality. The mechanisms that make longer birth intervals healthier for infants and mothers are difficult to identify. This is because many factors—such as the number of children a mother already has and her age at childbirth—influence birth intervals and affect child and maternal health independently. Also, a birth interval affects more than one child—the preceding child as well as the succeeding child—and either birth interval could be responsible for a child’s death (10, 45, 134, 201).

• Maternal depletion syndrome: A long-standing hypothesis contends that short birth intervals do not allow a mother enough time to restore her nutritional reserves after childbirth and breastfeeding (80). Although the role—or even the existence—of maternal depletion syndrome is not yet settled (67, 202, 203), recent studies confirm that short intervals affect mothers’ energy (107), weight (83, 171), and body mass index (83). A mother’s poor nutrition in turn affects fetal nutrition and growth (19, 81, 121) and thus infant survival (32).
• Premature delivery: Some studies find that shorter intervals are associated with an increased risk of premature birth (36, 56, 110, 213), but others have found no such association (51, 81, 94, 169). Both premature delivery and fetal growth retardation can result in low-birth weight babies, who are at greater risk of dying in infancy (210).
• Milk diminution: If mothers have their next child while they are beastfeeding, they are often less able to produce breast milk for the previous child (2). When children are weaned too soon, their growth suffers, they are more likely to suffer from diarrhoeal disease and skin infections (26), and they are thus at greater risk of dying (186). Milk diminution is more likely to occur as women have more children and are undernourished (57). The benefits of longer birth spacing do not diminish significantly when the length of breastfeeding is accounted for statistically, suggesting that birth spacing benefits children through other mechanisms in addition to allowing longer breastfeeding (112, 159).
• Sibling rivalry: When children are close in age, they compete for resources and for maternal care (128). Mothers may not be able to breastfeed the older sibling properly, either because her milk flow slows or because her time is taken up by the newborn. Mothers also may not be able to breastfeed the newborn properly, placing the newborn at higher risk for nutritional deficiency, infectious diseases contracted from older siblings, and other health problems as immunity declines (23, 165). It is unclear whether siblings’ competition for resources is important to explain the effects of short spacing, however. The risk of mortality for the older sibling remains the same when the newborn dies (42, 175), but the risk of mortality for the newborn declines when the older sibling dies (7) or when the older sibling is age five or older (159).

Harvey Nelson

In Zambia a woman breastfeeds her two children of different ages. Sibling rivalry begins at the nipple. When young children are close in age, they compete for maternal care and resources.

Why intervals longer than 5 years are less healthy. Little is known about why birth intervals longer than five years are less healthy for mothers and their children. The DHS and CLAP researchers suggest that, after five or more years of not having children, mothers may lose the protective benefits of previous childbearing, such as a reduced risk of pre-eclampsia and eclampsia. Thus they may be just as likely to experience the health problems associated with pregnancy as first-time mothers. Their children also could be just as likely to experience health problems or a higher risk of death as first-born children.

Many women in developing countries suffer from reproductive health problems—such as pelvic inflammatory disease and uterine fibroids—and are thus less fertile. These women may become pregnant only at lengthy intervals (95, 140, 193), and their higher risk for pregnancy complications could be due to underlying reproductive health problems, not because of longer intervals (1, 13, 20).