Florencia Torche: acute stress in-utero - can it damage baby's health and life chances?

In Episode 3 of the DIAL Podcast, Professor Florencia Torche from Stanford University talks about the impact of acute stress on a child's outcomes even if the stress occurs before they are born.

Florencia is a keynote speaker at the DIAL Mid-Term Conference 2019.

Transcript

Christine Garrington  0:00  

Welcome to DIAL a podcast where we tune into evidence on inequality over the lifecourse. In today's episode, we're asking whether and how acute stress might affect the lives of children, even if it's experienced in the months before they're born. I'm joined by Professor Florencia Torche from Stanford University who has been looking at links between environmental stressors and children's outcomes, and how these exposures contribute to the persistence of poverty across generations.

Florence Torche 0:28 

It is the case that children that who grew up in poverty are much more likely than our children to be exposed to a wide range of environmental stressors and toxins. This includes natural disasters and violence in you know, your neighbourhood or the wider context. It includes lead toxicity, neighbourhood conflict, and so on. Now, we know that all these exposures that children are affected to are bad for them have a handful effects on their health, on their education, on their development. Because of that, these exposures are more likely to result in disadvantage in later life, and therefore inequality. That provides a link for early exposures as early as before birth, and then poverty in later life, and the reproduction of poverty across generations, because the poor kids are much more likely to be affected by these environmental exposures. 

Christine Garrington  1:40  

So that's the background, what aspects of children's lives have you focused on specifically and why?

Florence Torche 1:45

My research has specifically focused on prenatal exposures, exposures that happened even before birth, and then whether or not and to what extent those prenatal exposures affects children's health, as early as when they're born. So measure, for example, through birth weight, gestational age, and then there are those children's health as they grow up and enter into adolescence, their cognitive development and their education. These outcomes are crucial research indicates very clearly for their wellbeing as adults, right for whether they're going to have a comfortable life? Whether they're going to have a sufficient level of economic wellbeing? So if we're able to understand how they develop early in life, we will have a very good, very precise indicator of how well they will fare in adulthood. This is all embedded in a, what we call a lifecourse perspective. Basically, you want to understand what happened to people very early in their lifecourses, in order to be able to better understand and predict what will happen to them as they age, as they grow up and become adults

Christine Garrington  3:07  

Understood. So you've undertaken some work in the last few years, looking at the impact of an acutely stressful event. In this case, what we're talking about is an earthquake has happened in Chile, on outcomes for children whose mothers had experienced the earthquake while they were pregnant. What was your thinking behind this research? 

Florence Torche 3:27

Researchers have claimed one important reason why poverty so bad for children is that it causes stress and stress disrupt development early in life. Well, that claim is very reasonable. It's certainly possible, but it hasn't been proven. So I thought, how can I prove that it is stress, and not other correlates or consequences of poverty, that is really bad children? Of course, stress is correlated with many bad things that happen to people, right. So what my task was as a researcher was to find some source of stress that was uncorrelated with other, you know, harmful exposures, what I was searching for was a so called natural experiment. So a setting in which stress happens at random, and that I found with an earthquake, we with current technology, we don't know when and where an earthquake will occur in this country. In that case, an earthquake provide something very close to an experimental design in the sense that women who had the bad fortune of being exposed to a particular earthquake are randomly allocated to an earthquake acid were right because they are no different from women living in some other region of the country, where the earth quake did not happen. And then what I did was to examine what happened with the babies who were born to the women who happen to be exposed to the earthquake and compare that to other women who were pregnant in the same country at the same time, but in a region that was not exposed to the earthquake, and I that provided my so called control group.

Christine Garrington  5:24

So in this instance, we were looking to see if there might be some link between pregnant mums who experienced an earthquake and the weight that their baby was born. So before you tell us what you found there, can you just explain why a baby's birth weight is an important measurement or indicator to consider when we think about how they might get on later on in life? 

Florence Torche 5:40

And also another important birth outcome present is a gestational age. In particular, whether the baby was born low weight - that's below 2500 grams - and whether the baby was born preterm – that is before 30 weeks of gestation. The reason to choose these outcomes is that they provide the very first measure that we researchers can observe of the baby's health and wellbeing. And based on recent research, we know now, these birth outcomes, they predict infant mortality and morbidity. And furthermore, they predict childhood in development, cognitive and social emotional development, they predict educational attainment, and they even predict outcomes in adulthood, they predict earnings, they predict income, they predict your ability to marry and form a family. They predict a wide range of outcomes throughout the entire lifecourse. So they provide a very powerful indicator of, you know, opportunities and endowments of individuals at the starting gate of life. I do not mean that someone who is for low weight is doomed to having problems at all, but they increase the likelihood of having developmental or educational, and even economic limitations in quite substantial proportion. So they provide at the population level, a very good indication of a certain limitation that we may want to prepare for and we may want to take into account. 

Christine Garrington  7:30

Right, so let's move on to the important stuff, what you found and what you think we learned from what you found?

Florence Torche 7:36

The women who had the bad fortune of being exposed to these sorts of acute stress, the earthquake had babies that were on average, of lower birth weight, and they were substantially more likely to be born low weight and to be born preterm. So when I compare the women who experienced the earthquake, and the women who did not experience the earthquake, but gave birth at the same time, there was a substantial difference in the proportion of low weight babies and preterm babies. These harmful effect of the exposure to the earthquake was very clearly concentrated on the first trimester of gestation. Only for those women exposed early in the pregnancy, we found such a harmful effect on birth outcomes. This research provides strong evidence that exposure to acute stress is bad for a infant health. And given that we know that infant health is predictive of development and wellbeing later on in life, prenatal exposure to acute stress may have harmful effects throughout those babies lifecourses. What my research suggests is that exposure to acute stress, even if short term might be bad for children, if it happens before birth.

Christine Garrington  9:08

In a follow up paper, you looked at the longer-term effects on children's cognitive abilities tell us what you did there.

Florence Torche 9:15

There isn't that we just discussed finds a negative effect of stress on birth outcomes. And like I said, birth outcomes predict later disadvantage. But, of course, we want to know if it is indeed the case that prenatal stress has accumulated effect on children as they grow up and they develop? So in order to address this question, I did this a follow up research in which I still use the earthquake. And I follow up kids over time, and I measure their cognitive development when they were about seven years of age. And what I found there was that exposure to the stress so in utero, so prenatally had a significant negative effect on kids’ cognitive development. But importantly, this effect manifested itself only among poor children, there was no effect among the middle-class children. So it was an effect that was stratified by socio economic advantage. And that emerged only among families that were in poverty. 

Christine Garrington  10:28

So in another area of your work also, in a similar sort of way, has focused on these stressful situations that migrants find themselves in the US, particularly in recent times where some states have introduced new and what some might describe as extremely restrictive laws aimed at curbing migration. Now, tell us what you were looking at there and why you moved on to this topic.

Florence Torche 10:52

I see this research on the effect of a prenatal exposure to these restrictive immigration laws as part of the same research agenda, which is to really try to understand whether these sources of environmental stress experienced before birth matter to people. Sitting here, as you mentioned, is very different. Now, I'm looking at one particular a very restrictive immigration law that was passed in the state of Arizona, in the United States. This law was passed in 2010, the law implemented a series of restrictions, attempting to make life so difficult for undocumented immigrants that they would, quote unquote, self deport that they would leave basically, that was the stated objective of the law. And my interest was to try to understand whether the passage of this law affected the health of babies of immigrants, but not only of undocumented immigrants, but also of the entire immigrant population, including documented immigrants, and even perhaps the Hispanic population in the United States. In that particular state that wasn't immigrant that was US born, that it may have failed, or be seen as very close to the immigrant population. This research was based on the birth records for Arizona, and four other states that are used as control states by, in this attempt to try to isolate the effect of stress for the babies that were in utero. During the passage of this law, there was a detrimental effect on birth outcomes, again, only for the babies of immigrant women in Arizona. I compare these effects with pregnancies of a US born black and white women, and there was no effect. So in fact, I was able to document an effect, a negative effect on the immigrant population. 

Christine Garrington  13:12

One very surprising finding from your research in this area was that babies whose mothers have been exposed to violence, obviously another form of acute stress, and in this case, Homicide in Mexico, were heavier on average than those who were not. And these experiences reduced the overall proportion of babies with a low birth weight. What do you make of that? Because it seems rather counterintuitive, especially after all this other evidence that you've, that you've, you've put together.

Florence Torche 13:43

What happened in Mexico, during a period after the year 2000 is that there was an enormous increase of drug trafficking related violence. So my question was, is the increase in violence affecting the health of infants that are born in Mexico? And to my surprise, mothers exposed to local violence were likely to give birth to babies that were heavier on average, and less likely to be low weight. We did the research several times to just make sure that this finding was indeed a true finding. And once we convinced ourselves, we find we search for explanations. Those mothers that were exposed to violence in their municipality, were much more likely to seek prenatal care. It was the benefits of prenatal care that were able to more than compensate for any negative effect of violent exposure. Specifically, those moms who were exposed to violence started prenatal care areas and went to the doctor more often. It really captures the agency of women, in this case pregnant women, right. We just documented one mechanism that we may use to protect their pregnancy. Secondly, we found this effect only among poor women living in urban areas. And the reason is clear to see once you think about it, first of all, among more advantaged women, they were all using prenatal care. So there was less room for they increase use, right. So it was the poor women who, prior to exposure to violence, were may have not gone to the doctor early in their pregnancies who decided to do so. But only in urban settings, because in the Mexican case, in rural settings, they access to health care, and in this case, to prenatal care, it's very limited. So even if they wanted to go It was much more difficult to them, we may not be able to reduce substantially the exposure to stress, I mean, stress has happened in people's lives. And it may they may continue to happen even if we try to reduce them and even if we're successful person, but even so, if we are able to provide easy access, quick access to prenatal care of high quality, we may be able to at least counteract to some extent the noxious effects of a stress exposure.

Christine Garrington  16:39

I just before we sort of really wrap up and talk about the broader policy implications of your research, I want to ask you about one more bit of research that you did, where you looked at, where mothers have been caught up in a war situation. And once again, looked at the impact of that or the ramifications of that to the birth weight of their children. Tell us what you found there. 

Florence Torche 17:00

This research was conducted in in Israel in the northern part of Israel, in context of a of an armed conflict in which people who are living in northern Israel were vulnerable to missiles coming from across the border. So the babies born in that area after the war, were more likely to be low weight and preterm than babies born before or after, or in other regions of the country, suggesting once more that it is the exposure to acute stress that caused this decline. In in both a birth weight and gestational age, the actual damage of the missiles was extremely limited. In fact, virtually no missile landed in the area. So this provides clear indication that it was stress and not the actual consequence of the missile that produced the damage.

Christine Garrington  18:03

Florencia this is an important and fascinating body of work that you've done, what would you say, as a whole, it tells us about how this acute stress is acutely stressful events, impact on children's lives and also for what it means for how they will fare later on in life compared with those children who've had more of a stress free path into life. And certainly through the first few months and years of their life. What have we learned?

Florence Torche 18:30

We have now very persuasive evidence that stress experienced before birth has long term consequences we have clearly documented an affect in birth outcomes. And now my recent research documented an effect on cognitive ability and then subsequent educational attainment. Those early outcomes are so predictive, predictive of economic wellbeing later in life that we have a unfortunately, quite clear evidence that the children who have the bad fortune of being exposed of stressors before birth, may have trajectories that are more disadvantage than their peers. That they're they they're more likely to have developed health, developmental, and socio-economic limitations later in life. These to me highlights the relevance of including the prenatal period when we consider population health. The prenatal period is very easily neglected and forgotten. Because it's invisible. Unless we search for exposures before birth, we're not going to find them, but they're going to be consequential for the health and wellbeing of the next generation. So, in my view, my research and that of others, really highlights the importance of looking for these potentially harmful exposures that may happen even before birth, and to try to implement to the extent that is possible with policy strategies to try to compensate for the disadvantages that these exposures cause. It's not that we're gonna create a stress-free world, but we can certainly develop policies to try to compensate for the harmful effects of stress that are experienced even the solvency of 

Christine Garrington  20:27

Florencia Torche is one of the keynote speakers at the Dynamics of Inequality Across the Lifecourse midterm conference in June 2019. More information is available on the DIAL website at www.dynamicsofinequality.org. Thanks for listening to this episode of our podcast, which is presented and produced by Chris Garrington and edited by Elina Kilpi-Jakonen.