Pregnant women who are exposed to neighborhood violence during their first trimester have a greater risk of having a low birth weight baby due to an earlier delivery, according to researchers at Queen Mary University of London and the University of Leicester.
For the study, the researchers looked at the birth outcomes of Brazilian children whose mothers were exposed to local violence as measured by homicide rates in small Brazilian municipalities and the neighborhoods of the city of Fortaleza.
The researchers compared the birth outcomes of mothers who were exposed to a homicide during pregnancy to otherwise similar mothers living in the same area, who happened not to be exposed to homicides.
“Our results have the potential to generalize to other settings where violence is endemic, as is true for many middle and low-income countries in Latin America and Africa. The results presented shed light on the additional cost of violence, largely ignored previously, in these countries,” said Professor Marco Manacorda at Queen Mary University of London.
The findings show that birth weight drops significantly among newborns whose mothers had been exposed to a homicide during pregnancy. Importantly, these effects are linked to the first trimester of pregnancy, which is consistent with claims that stress-induced events matter most when occurring early in pregnancy.
“We provide evidence that these effects on birthweight are driven by prematurity rather than growth retardation of full lengths pregnancies, in line with evidence from the medical literature,” said Dr. Martin Foureaux Koppensteiner at the University of Leicester’s Department of Economics.
Specifically, the researchers found that one additional homicide in small municipalities during the first trimester leads to a reduction in birthweight of around 0.59 ounces. One extra homicide leads to an increase in the probability of low birth weight by 0.6 percentage points, an 8% increase compared to baseline.
Results for the neighborhoods of Fortaleza, where homicides are much more common, are considerably smaller (around 15 percent of the effects for small municipalities), which is consistent with the interpretation that violence is more stressful when it is rare.
Because of the extremely high levels of violence in Fortaleza, the researchers calculated that homicides account for approximately one percent of the incidence of low birthweight and 3.5 percent of the incidence of very low birthweight.
“As the mothers examined in the study are likely to live in very similar environments, by exploiting the precise timing of the occurrence of homicides we are able to disentangle the causal effect of homicides from other correlated effects that may otherwise bias these estimates,” said Koppensteiner.
“We also find that socio-economic factors, such as the mothers’ low level of education appear to amplify the adverse consequences of violence on birth outcomes, implying that violence compounds the disadvantage that newborns from low socio-economic status already suffer.”
The findings are published in the Journal of Development Economics.