Native-born mothers in US show higher infant mortality rates

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California researchers find that several factors, including social experiences, can negatively impact pregnancies

Researchers at UC Davis and the University of North Carolina have found that mothers born outside the U.S., across many races and ethnicities, have lower infant mortality rates (deaths per 100,000 infants) than mothers born inside the U.S. when both groups give birth within the United States.  

The study used data from developed and developing areas like China, Japan, Mexico and broader ethnic groups like Hispanics, Native Americans and Asian-Pacific Islanders. With this wide collection of infant mortality rate data, the trend showed that regardless of race/ethnicity — with exception for women born in Puerto Rico — all women immigrating into the United States had better infant health outcomes and therefore lower IMRs than their native-born counterparts.

Countries are classified based on income levels. Western Europe, Australia, New Zealand and the United States are some of the areas considered developed, or high income, by the United Nations’ standards. On the other side of the spectrum sit countries experiencing lower income which are therefore considered developing countries, such as regions in Africa and Asia and all of Central and South America.

It is typically assumed that within developed countries, health standards are higher with lower mortality rates than in developing areas. But this is not the case in the U.S.

“[This] is a major issue within the United States and we’re seeing that reflected in infant mortality rates, as well as disparities in maternal mortality rates,” said Mellissa Withers, an assistant professor at the University of Southern California’s Institute for Global Health. “That definitely highlights some major problems in terms of maternal care — prenatal, delivery care, post-partum care.”

Maternal and infant care is not the only area in which the United States performs poorly as a country. When compared to other developed countries, it performs the worst across all categories of health. This includes longevity, infant mortality, and rates of chronic diseases such as cardiovascular disease, diabetes and obesity.

Ultimately, it seems that healthier populations are the ones seen immigrating. Erin Hamilton, an associate professor of sociology at UC Davis and one of the researchers on this study, mentioned that mothers coming from countries outside the U.S. are not representative of their populations of origin.  

“We observed the trend across people of different national origins and racial and ethnic backgrounds,” Hamilton said. “Immigration is so costly and difficult that it selects on a healthy, robust group of individuals who are able to afford and take the risks that are involved with immigration internationally.”

But why are mothers in the U.S. performing so poorly? Nicole Smith, a UC Davis alumna and a public health nurse, found similar results during her master’s thesis three years ago looking into maternal and health outcomes in disadvantaged communities.

“Black women have two to three times the infant mortality rates of women of other races,” Smith said. “It doesn’t really matter where you look across the United States — if you look different states, you’re going to find that black women have worse birth outcomes than white women.”

Population health scientists have looked deeper than the external biological factors that affect human health.

“[Many] factors influence a woman’s health, often starting very early on,” Withers said. “Even before she is born but certainly all the way through childhood and these different exposures that happen throughout the stages of life have a cumulative effect on you.”

Known as the social determinants, they take into consideration multiple levels of factors that influence the health of an individual.

Socioeconomic determinants, made up of factors such as wealth and education, control one’s ability to limit exposure to pathogens, development of illness and even access to treatment. Environmental controls such as water sanitation systems or vaccinations help prevent the risk of contamination that leads to illness and is the next social determinant. Personal preventative measures are the means by which an individual’s actions can reduce the risk of illness, through practices like washing hands, eating well and exercise. When already exposed or at risk to disease or malnutrition, the next determinant at play is therapeutic interventions like surgery, antibiotics and other medical treatments.

Do these determinants play a role in infant mortality?

“There’s all kinds of more fundamental causes of health that precede whether or not you go to the doctor,” Hamilton said. “Even with something like pregnancy which isn’t really a health problem, what’s going on with a pregnancy has more to do with the environmental conditions that you live in, your health behaviors, and your socioeconomic status.”

Smith argued there might be yet another factor behind these poor health outcomes. Recently, more research has gone into studying the impacts of racism on health and have concluded that individuals experiencing racism or even perceived racism can lead to poor health.

Published in 2017, some of Hamilton’s results showed that black women born outside the U.S. have IMRs of 9 per 100,000 births and those born inside the U.S. have IMRs of over 13 per 100,000.

“It can be racism the woman has experienced starting from when she was born or when she was in utero and her mother’s racial stress triggers over time cause this affect that can cause worse health outcomes, including birth outcomes,” Smith said. “The service black women receive is not the same as women of other races, and there is racism in the health care they receive while they’re pregnant and that impacts the birth outcome.”

All in all, it seems that there is no single explanation to this phenomenon. Whether it’s the environment negatively impacting the mothers, racism or the U.S.’s complicated healthcare system, it seems that all these factors place a toll on health outcomes.

“Women, for example, in Texas, if you isolate that group, have maternal mortality rates that are much worse than even some countries that have much lower incomes,” Withers said. “That highlights a gap, a racial and ethnic gap in terms of maternal mortality. And obviously, infant mortality is very much related to the care that women get during pregnancy.”

Access to clean water and healthy food, things many people might take for granted are not guaranteed for everyone. And the lack of access can lead to dramatic health issues.

“Our healthcare system is very much focused on reacting, after the fact when someone is already sick,” Withers said. “Instead we should really be focusing much more on preventing these conditions and diseases to begin with.”

Hopefully, with more research combining social views with hard science, more light will be shed on the problem.

“We have a cultural idea in the U.S. that medicine is the best solution to all kinds of problems, even though a lot of our problems are social,” Hamilton said.

 

 

Written by: Alice Rocha — science@theaggie.org