Elisa Martins
Journalist, special for Yvirá
In the 1980s, only 20% of Brazilian municipalities experienced heat waves, meaning temperatures above 35 degrees Celsius for at least three consecutive days. Today, that figure reaches 60% of the country’s municipalities.
Through scores and behavioral risk classification, the results showed that each additional day of heat exposure during pregnancy was significantly associated with greater irritability and greater difficulty reported by mothers with the babies’ routines.
Our perception is that these are problems that may become even more significant in the future and affect school performance.
It’s no use just looking at the child who is already in school. Taking care of the mother’s mental health is also a strategy to protect child development.
Elisa Martins
Journalist, special for Yvirá
JUNE/JULY 2026 | n.º 7 | Researcher explains how both prenatal exposure to heat waves and maternal depression can impact children’s behavior and school learning
PHOTO: PERSONAL ARCHIVE
Climate emergency affects populations, ecosystems, and threatens the environmental balance on the planet. It can also have a broad effect on child development and school performance, as shown in a study developed by economist Naercio Menezes Filho, professor at the Ruth Cardoso Chair at Insper and at the Faculty of Economics, Administration, Accounting and Actuarial Science at USP, in collaboration with researcher Bruno Kawaoka Komatsu, also from Insper.
In the 1980s, only 20% of Brazilian municipalities experienced heat waves, meaning temperatures above 35 degrees Celsius for at least three consecutive days. Today, that figure reaches 60% of the country’s municipalities.
The research focused on the association between exposure to heat waves in the womb and outcomes in child development and behavior. Although previous studies have already linked prenatal heat exposure to adverse birth outcomes, as Naercio Menezes Filho explains, little is known about its implications for child development, especially regarding early behavioral regulation beyond the neonatal period, with potential impact on future school learning. “The study shows that if we want a healthy child who learns, we have to worry about the mother, even more so in a world in climate crisis. It’s no use just looking at the child who is already in school,” says the researcher. Check out the interview below.
Through scores and behavioral risk classification, the results showed that each additional day of heat exposure during pregnancy was significantly associated with greater irritability and greater difficulty reported by mothers with the babies’ routines.
The increase in heat waves is one of the most visible effects of the climate crisis today. Why should pregnancy be seen as a particularly vulnerable period to this phenomenon?
Our perception is that these are problems that may become even more significant in the future and affect school performance.
NAERCIO MENEZES FILHO: Scientific data shows how heat waves have increased in recent years. In the 1980s, only 20% of Brazilian municipalities experienced heat waves, meaning temperatures above 35 degrees Celsius for at least three consecutive days. Today, that figure reaches 60% of Brazilian municipalities. And pregnant women are particularly affected, given the number of physiological changes that occur during pregnancy so that the mother can support the placenta, the baby, and the growing baby’s own heat production. This affects the mother and, as we showed in the study, the effects also extend to the children. It is a very sensitive period.
It’s no use just looking at the child who is already in school. Taking care of the mother’s mental health is also a strategy to protect child development.
What does the scientific literature show about the relationship between extreme heat during pregnancy and child development? And how does the current study advance in this regard?
NMF: There are already studies showing the effect of climate change on child development, focusing on indicators at birth. For example, we already know that there are impacts on gestation time, which can be shortened, and on the baby’s birth weight, which can be below average. But few studies investigate the effect of heat waves during pregnancy on the later development of children, or they end up focusing more on issues such as nutrition and epidemiology. Our cohort study focuses on child behavioral outcomes, with follow-up by psychologists and other specialists. Our research progressed until the children examined were 18 months old, and the idea is to continue studying the impacts on this generation. We want to know if these effects continue after this phase and if they affect learning at school age.
How was this measurement done, and what were the main effects identified that can be associated with exposure to heat waves during pregnancy?
NMF: Our goal is to understand why children learn so little in public schools. Illiteracy is still very high among 8-year-old students, and difficulties persist in middle school. There are studies that focus on school conditions, family income conditions, and the conditions of education itself. But we have literature that shows that the first six years of life are fundamental in human development and form the basis of cognitive and socio-emotional skills. We decided to associate climate change with this set of influencing factors, seeking to understand if the developmental problems identified in this context can affect learning later. Prenatal exposure to heat waves was measured using climate data linked to maternal residential addresses. We collected daily satellite information that measures the temperature within a radius close to the homes of the mothers in the study. Our study is centered in Ribeirão Preto, state of São Paulo, but many hospitals in the city receive children from other regions. Based on temperature data related to the maternal residential region, we analyzed children who experienced heat waves while in the womb. Through scores and behavioral risk classification, the results showed that each additional day of heat exposure during pregnancy was significantly associated with greater irritability and greater difficulty reported by mothers with the babies’ routines.
Maternal depression appears as another indicator in the analysis of these effects of heat exposure on child development. How was this mental health factor associated with the study?
NMF: Mothers who have depression before pregnancy tend to have depression afterward as well. And it seems that heat waves are impacting this condition, both during pregnancy and in the months following the baby’s birth. In the study, we examined maternal depressive symptoms as a possible mediating pathway linking infant outcomes to prenatal heat exposure. Our analyses indicated that maternal depressive symptoms accounted for 21 to 33% of these associations. These findings highlight early behavioral regulation as a particularly sensitive domain in the context of prenatal heat exposure and emphasize maternal mental health as an important pathway through which climate-related stressors can influence early child development. We know that, lacking normal mental health, mothers may have more difficulty engaging in activities with their children, stimulating them, talking to them, and interacting with them. The numbers are not negligible; on the contrary, one-third of the children we monitor are at risk of developmental delay and already demonstrate behavioral issues such as inflexibility, irritability, and difficulties with routines. Our perception is that these are problems that may become even more significant in the future and affect school performance.
Does this impact on the child occur more due to biological exposure to heat or due to maternal mental health? Or due to a combination of both factors?
NMF: Due to a combination of both. There is an effect from the heat waves, but maternal depression also influences the child’s developmental indicators. Our first study already showed that heat waves influence the baby, which can lead to premature birth, lower weight, smaller head circumference, and congenital anomalies. And this can likely affect the child throughout their life. Now we show that maternal depression, in the context of heat waves, but also without them, affects irritability and difficulty with the babies’ routines. Despite our focus on the topic, heat waves are not the only factor that causes mental health problems. But I was impressed to find, based on our study, that 40% of mothers already had a diagnosed mental health problem before pregnancy. Most were anxiety and depression crises, all diagnosed. Many took medication. It’s a generation that is very affected. The study shows that if we want a healthy child who learns, we have to worry about the mother, even before she gives birth. It’s no use just looking at the child who is already in school. Taking care of the mother’s mental health is also a strategy to protect child development. Even more so in a world in a climate crisis.
Heat waves do not affect all people in the same way. What is the risk of the climate crisis widening existing inequalities in child development?
NMF: Clearly, families with better socioeconomic conditions are better prepared to deal with heat waves. Vulnerable families will have more difficulty having air conditioning at home, taking their children to study in a daycare with air-conditioned space, gardens and trees. The climate factor is another one that weighs on inequality. That’s where the role of public policy comes in. Municipalities and governments must start worrying about this. And in that case, creating warnings, bulletins, apps, that is, various ways to alert mothers and, especially pregnant women, a few days before the arrival of a heat wave. It is a preventive measure so that these women can protect themselves and their children, whether at home, at school, at a relative’s house, somewhere with access to water and hydration. It is necessary to offer advance notice and predictability so that precautions can be taken.
This is a topic that is still little discussed outside academia. Why should it be at the center of public policies on health, education, and climate?
NMF: Much more needs to be done. It is impressive how mankind is not taking the necessary measures regarding climate change. We experienced those floods in Porto Alegre, which destroyed a large part of the city, and then people returned to “normal,” as if nothing had happened. Like our study, there are others that show the cost of these heat waves and climate change for people of all ages. Science is warning us, based on studies and data from experts. This may be news that people don’t want to hear. But things won’t improve on their own; on the contrary. Without action from society itself and without public policies, they will only get worse.
