The effect of infant and child mortality on fertility is estimated using World Fertility Survey (WFS) data for 25 developing countries. The estimates reviewed show substantial variation across countries and by the technique used. Estimation with regression gives higher estimated effects than differences between mean or median birth intervals following the birth of a surviving child and those following an infant death. For women who breastfeed, the prevention of 1 infant death averts between .016 births in Trinidad and .351 births in Lesotho, with an average of .23 for neonatal and .17 for postneonatal deaths. Couples with an infant death appear to have between .138 more births in Sri Lanka and .808 more births in Syria, with an average of .484 more births than those who do not experience such a death. The estimates of births averted through the effects of mortality on the birth interval are close to what is generally reported in the literature, but the effects of a child death on subsequent fertility are substantially higher, perhaps because regressions give a better estimate of the true effect or because of the higher quality of WFS data. Of the 16 countries where comparisons were possible, the cost of averting a birth indirectly by averting an infant death were, on average, more than 10 times higher than the cost of averting a birth directly by family planning. Only in 1 country, Kenya, was mortality reduction clearly more cost-effective for reducing fertility than was family planning. The Kenya case might be replicated in other high mortality African countries if data were available. - See more at: http://www.popline.org/node/393910#sthash.fBe3Jl9e.dpuf