Her study, which also reported a higher proportion of babies with lower birth weights in the earthquake-affected regions, points to a less visible, though pronounced, impact of natural disasters.
“This research highlights an important, generally overlooked, consequence of natural disasters,” observed Torche. “It suggests that in-utero exposure, particularly in early stages of the pregnancy, may have long-lasting consequences on those not yet born, compromising their long-term attainment and well-being.”
“Low birth weight is the leading cause of infant mortality and of health and developmental problems during infancy and childhood,” she added. “But birth weight is correlated with more than health outcomes-it also affects cognitive skills, educational attainment, employment, earnings, and even the birth weight of the next generation.”
In order to isolate the effect of a natural disaster on birth outcomes, Torche examined two sets of infants: those who were in-utero in the areas in which there was pronounced destruction and infants who were in-utero in the same period, but whose mothers were in unaffected areas of the country. In addition, because a natural disaster may have different effects depending on the gestational period of exposure, Torche accounted for exposure across three trimesters of gestation.
By measuring birth outcomes for infants born before, during, and after the earthquake, as well as those born within and outside the affected regions, and controlling for maternal and county-level characteristics, the study isolated the effect of exposure to the catastrophe from other determinants of birthweight.
The findings showed a large detrimental effect of being in-utero during a major earthquake. The infants exposed to the earthquake during their first trimester of gestation had much higher chances of being born premature – 8 percent of those born during the earthquake, compared with about 5 percent of those born before and after in the affected region. By contrast, the group of infants not exposed to the disaster was unaffected.
Not surprisingly, this effect translates into an increased risk of low birth weight. Torche’s findings showed that the proportion of babies in the affected areas with low birth weight jumped to 6.5 percent from Chile’s normal rate of about 4.5 percent. Again, this effect was concentrated in the first trimester of gestation. By contrast, there was no change in the rate of low birth weight infants born in regions unaffected by the earthquake. The study also found that both prematurity and low birth weight returned to their normal values among the babies conceived after the earthquake.
The study relied on the birth registry database in Chile, produced by the Ministry of Health and the National Statistics Office, for the years 2004 through 2006.
“In contrast to the 2010 disasters, the Tarapaca earthquake took a relatively smaller toll in terms of human lives, injuries, and displacement,” Torche observed. “The recent and more devastating earthquakes in Chile and Haiti likely had a more harmful effect on birth outcomes.”