Collateral Damage and the Coming Immigration Raids

A report from the San Francisco Gate indicates that immigration officials may soon try to arrest up to 1,500 undocumented people in the Bay Area of California (“Feds planning massive Northern California immigration sweep to strike against sanctuary laws”). If true, it is likely to have an effect on the wider community.

A 2017 study by Nicole Novak and colleagues looked at the effects of a major government raid against migrant workers in Postville, Iowa — most of whom were Latino — who were suspected of being undocumented (Novak et al 2017). In May of 2008, nearly 400 workers were arrested at a meat-processing plant in Postville by 900 ICE agents in a surprise raid that used military tactics, including a Black Hawk helicopter. Two hundred and ninety-seven people were eventually deported after a five month prison sentence. However, even those who were not deported (or even arrested) were affected.

Novak et al. looked beyond Postville for their sample, including 52,344 births across Iowa from 2007 to 2009. Infants who were born in the 37 weeks following the raid were classified as being prenatally “exposed” to the raid’s effects. The results showed that for White and Latina mothers, rates of low birth weight (LBW) were steady before the raid. However, after the events at Postville, LBW rates increased by 24%, though only among Latina mothers. This was true for both foreign-born and U.S. born Latinas and their infants, showing a widespread effect that was due to ethnicity, rather than immigration status. The effect appeared to be greatest among those mothers who were exposed to the raid in the first trimester.

From Novak et al. 2017. Rates of LBW in three groups of mothers/infants in Iowa: Whites, U.S. born Latinas, and foreign-born Latinas.

Because data were only available at the state rather than local level, Novak et al. were unable to determine if rates of LBW were even higher among Latina mothers who lived closer to Postville than those in more distant parts of the state. However, the authors reasoned that Latina mothers throughout Iowa (and possibly outside of the state as well) were likely aware of the raid, either through following the news or direct communications with friends and relatives. Given that rates increased among U.S. born and foreign-born Latinas, it is certainly possible that Latina mothers felt vulnerable or anxious about raids targeting them for their ethnicity, and that the stress from this could trickle down to their infants.

If the raids in the U.S. continue, like the one apparently planned in California, there will likely be more collateral damage in terms of the health of Latina mothers and the development of their future infants, including those who are U.S. citizens. Furthermore, there is evidence that poor early development in life can have lasting health deficits. Somewhere in the debates about undocumented immigration, that should be factored into the equation of things to weigh. 



Novak NL, Geronimus AT, Martinez-Cardoso AM. 2017. Change in birth outcomes among infants born to Latina mothers after a major immigration raid. International Journal of Epidemiology. 46(3): 839-49. Link

Prenatal “Shocks” and Birth Outcomes

Birth weight is often used as a rough gauge for the quality of the prenatal environment. A newborn who weighs 2500g or less (about 5.5 pounds) is considered to be “low birth weight” (LBW). At the individual level, weight alone is an imperfect measure because of confounders such as gestational length (it’s axiomatic that the less time spent in the womb, the less time there is to grow). However, at the population level, if average birth weight fluctuates, then it is an indication that something in the environment probably has changed.

Sometimes, stressful changes can be low-intensity and chronic; at other times, they can be abrupt and dramatic. Biologists, psychologists, and bioanthropologists might call these changes “stressors” or “insults.” Economists might use the term “shocks.” They’re both getting at the same idea: to what extent can harmful environmental factors affect growth and health outcomes? 

In the case of a natural disaster, the harm done can be substantial. Florencia Torche (2011) found that rates of LBW increased following the 2005 Tarapaca earthquake in northern Chile. Despite the magnitude of the earthquake (7.9 on the Richter scale), the amount of destruction was relatively limited: eleven people died, and 0.035% of the population had to temporarily relocate to shelters. This was attributed to the low population density of the region as well as Chilean preparedness and building codes to withstand earthquakes. Although the damage was not as severe as it could have been, Torche reasoned that the earthquake likely caused acute maternal stress, which in turn could affect prenatal development. 

Looking at over half a million births, Torche used maternal county of residence as an estimate of the earthquake’s intensity across different trimesters of exposure. She found that mothers who were lived in the most intensely affected regions during the first trimester were the most affected. The probability of LBW increased from 4.7% to 6.5%, while rates of pre-term births also increased from 5.2% to 8.0%. Later periods of gestation were not substantially affected, and for infants who were conceived after the earthquake, the probability of LBW returned to baseline.

Again, these outcomes seemed to result primarily from acute psychological stress stemming from the earthquake. Torche reasoned that – given the relatively low amount of damage to infrastructure – the increases in LBW and pre-term births were unlikely to have resulted from other factors such as malnutrition, infection, stress resulting from deprivation, strenuous workloads, or exposure to environmental toxins. In reality, it’s not possible to control for all of these variables entirely, but overall it seems plausible that maternal psychological stress played a substantial role in birth outcomes.

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