The Impact of Transitory Income on Birth Weights: Evidence from a Blackout in Zanzibar

Do transitory income shocks affect infant health? I find evidence that birth weights fell following a temporary income reduction caused by an unexpected, month-long blackout in Zanzibar. Relying on 350 household surveys collected during field work, I show that the 2008 blackout reduced labor supply of workers in electricity-dependent jobs by an average of 25%, with no effect on workers in other sectors. The income shock was temporary. Using over 20,000 birth records from a maternity ward, I document a reduction in the average birth weight of children exposed to the blackout while in utero, and an increase in the probability of low birth weight. Supporting a causal interpretation of these results, the reduction in weights is correlated with measures of maternal exposure to the blackout. In particular, reductions in birth weights were largest among children from wards with intermediate levels of employment in electrified sectors. The two causes that are most consistent with these results are a blackout-induced decline in maternal nutrition, and maternal stress. Alternative explanations are examined, including the possible effects of a temporary fertility shift. It is shown that the blackout increased births, but that selection into pregnancy cannot explain the drop in birth weights.