On tap: a shorter trip to get water boosted the birth rate in Ethiopian villages.© WHO

Improving access to clean water can cause unexpected health problems, suggests a study in Ethiopia.

Cutting down a woman's long trek to get water can boost her fertility. But bumping up birth rates worsens childhood malnutrition overall.

It is widely accepted that a cleaner water supply will enhance the health of those in developing countries. But few studies have tested how such installations affect a village as a whole.

Two UK researchers examined what happened after water taps were plumbed into several rural villages in southern Ethiopia between 1996 and 2000. They gathered information on children's births and deaths before and after the water supply arrived, and compared the data to that collected from settlements without a new tap.

Weighed down

As they expected, the taps slashed the death rate among children by half, at least partly because they cut infectious diseases spread in dirty water. More surprisingly, the pair found that women were, each month, three times more likely to give birth in the years after the tap was introduced. Mhairi Gibson of the University of Bristol and Ruth Mace of University College London, both in the UK, report their findings in Public Library of Science Medicine¹.

The increase in birth rate did not seem to be explained by factors such as changes in the women's age, overall health or prosperity. The researchers suggest that the women's fertility may have soared because they had stopped burning up energy trekking to and from distant water supplies. The women had previously spent up to six hours per day fetching water in extremely heavy clay pots. "I could barely lift an empty one," Gibson says.

The women's fertility may have been partly dampened by this strenuous exercise, says Gibson, much as athletes often experience a drop in fertility from excessive training. When the women had to walk only 15 minutes to a village tap, their fertility shot up.

More mouths to feed

This boost in birth rate takes a toll on children's health. The investigators found that kids were more likely to be malnourished, based on their height and weight, in villages with taps than in those without.

This could be simply because families are sharing their scarce food between more children. Or perhaps low birth-weight babies, who previously would not have survived the trauma of birth, are now surviving but not thriving.

The higher birth rate might help explain why rural Africa's population continues to spiral upwards despite slowly improving living and health conditions, Gibson says. It contrasts with the rapid drop in birth rates seen in developed countries as economic conditions improve and family planning becomes more widely used.

Gibson says that aid agencies and other organizations that promote access to clean water may overlook the effects on birth rate.

She argues that new taps, or other development schemes, should ideally occur in parallel with increased access to contraception and child healthcare. "It's something these organizations haven't really looked at," Gibson says.

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• References

  1. Gibson M. J.& Mace R. PLoS Medicine, 3. e87 (2006).