Association between socioeconomic status with birth outcomes and infant growth in the first two years of life: case study in South Africa and democratic Republic of Congo
Date
2020
Authors
Ngandu, Christian Bwangandu
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Background: Lower socioeconomic status has been associated with impaired child growth
globally, but there have been limited literature and lack of consensus of the evidence on the
relationship between socioeconomic status (SES) factors and infant growth in sub-Saharan
Africa (SSA). Therefore, the aim of this thesis was to investigate the relationship between the
household and maternal demographic as well as SES factors including maternal education;
occupation; income; marital status; and household wealth index (HWI]), and adverse birth
outcomes and infant undernutrition from birth until age two years in SSA.
Methods: One theoretical and two empirical studies were conducted to achieve the aim of this
thesis. Firstly, a systematic review, following the PRISMA guidelines, combined the existing
evidence on the association between SES factors and birth outcomes, including low birth
weight (LBW), preterm birth (PTB), small for gestational age (SGA), and growth outcomes
including stunting, wasting and underweight in children younger than 24 months in SSA
countries. Secondly, in a cross-sectional comparative study, the associations between SES
factors and birth outcomes in the Democratic Republic of Congo (DRC) and South Africa (SA)
were compared in newborns at birth (ranged from 0 to 2 days). Thirdly, a cross-sectional
analysis, drawing data from a longitudinal study which is referred to as the Soweto Baby
WASH, investigated the associations between SES factors and undernutrition from 0 to 12
months in infants born and living in Soweto in SA.
Results: Overall, the thesis highlighted that maternal education and household wealth, as major
SES factors, were associated with nutritional status in children at birth and during the first two
years of life. Findings were threefold: Firstly, in the systematic review, a lack of consensus on
the definition of ‘SES factors’ made comparison and generalisability of the evidence
challenging. However, lower HWI, maternal unemployment, and low maternal education were
consistently shown to be SES predictors of adverse birth outcomes (LBW, SGA), and infant
undernutrition (stunting, wasting, and underweight) in SSA. Secondly, the local/regional
context matters when assessing the association between SES factors and infant growth. Living
in SA as compared to the DRC was associated with reduced odds of a newborn to be LBW,
PTB or SGA, which reflects country-specific differences in maternal and household resources
as well as social position (education access, housing, marriage). Being married in the DRC was
associated with decreased likelihood of having LBW and PTB newborn whilst South African
mothers with secondary level of education and above experienced lower risk of having a SGA newborn. Thirdly, living in a wealthier household was associated with higher weight-for-height
Z-scores and associated with lower height-for-age Z-scores at twelve months. However, living
in a poor household with mother who had a secondary level of education and higher was
associated with greater linear growth and lower weight gain at twelve months in SA. Maternal
income, occupation and marital status were not significantly associated with infant growth in
Soweto, in, SA.
Discussion: Maternal level of education, marital status, and household wealth were associated
with growth and nutritional status from birth to two years of age in SSA with country
disparities. These disparities were based on the level of socioeconomic development across
different countries in SSA. In addition, maternal biological and country factors were strong
predictors of infant growth and nutritional outcomes as they underpin individual and household
capabilities. In wealthier households, infants gain weight compared to their height in the
nutrition transition context like in South Africa.
Conclusion: Social policies should protect single women who are socially and economically
deprived before, during, and after pregnancy to improve maternal and child health and
nutrition, and to optimize their intergenerational influences.
Keywords: Socioeconomic status, birth outcomes, infant growth, undernutrition, sub-Sahara
Africa, the Democratic Republic of Congo, South Africa
Description
A thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy to the Faculty of Health Sciences, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, 2020