Effects of Birth Month on Child Health and Survival in Sub-Saharan Africa

Abstract

Birth month is broadly predictive of both under-5 mortality rates and stunting throughout most of sub-Saharan Africa (SSA). Observed factors, such as mother’s age at birth and educational status, are correlated with birth month but are not the main factors underlying the relationship between birth month and child health. Accounting for maternal selection via a fixed-effects model attenuates the relationship between birth month and health in many SSA countries. In the remaining countries, the effect of birth month may be mediated by environmental factors. This study found that birth month effects on mortality typically do not vary across age intervals; the differential mortality rates by birth month are evident in the neonatal period and continue across age intervals. The male-to-female sex ratio at birth did not vary by birth month, which suggests that in utero exposures are not influencing fetal loss, and that therefore the birth month effects are not likely a result of selective survival during the in utero period. In one-third of the sample, the birth month effects on stunting diminished after the age of 2 years; therefore, some children were able to catch up. Policies to improve child health should target pregnant women and infants and must take seasonality into account.

Notes

¹ Historically, measles was also a leading cause of childhood deaths, but its contribution has declined significantly in the last decade.

² A child is considered stunted if his or her height for age is more than two standard deviations below the mean in the World Health Organization’s reference population. Malnutrition, infections, stress, and genetic disorders can all lead to stunting. Height faltering is usually observed after the weaning period and is thought to be indicative of chronic malnutrition and disease status; therefore, it does not fluctuate widely over time. However, stunting can have its antecedents in fetal development; in those cases, it is typically described as “small for gestational age” (McCowan et al. 1999; Maleta et al. 2003).

³ The Cox PH is one of the few survival models that can incorporate both random effects and fixed effects. To run a fixed-effects model, I stratified the data by maternal identity and removed variables that were fixed for mothers over time (Skrondal and Rabe-Hesketh 2012).

Additional information

Funding

I was supported by the National Institute for Child Health and Human Development, Grant No. R24HD047879, to the Office of Population Research at Princeton University. I was also supported by a NICHD Grant No. R24HD041023, to the Minnesota Population Center at the University of Minnesota. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.