Having a child between 42 and 44.5 reduced annual mortality by 7 percent, and it was 17 percent lower for women who had a child at 44.5 years of age or later.

Brazil, the world's fifth most populous country, ranks also fifth in terms of annual road traffic mortality with 18 deaths per 100 000 inhabitants, according to WHO.

He argues that the fall in child mortality should be calculated over a slightly longer period, so the annual fall works out at 5.9%, not 7.8%, as in the Lancet.