We are now living in a world that is, on average, nearly 1.5°C warmer than the pre-industrial period. Every year, new records are being set across the world as heatwaves become more frequent and more intense, as a result of human-induced climate change.
However, climate change is not just an environmental crisis; it’s a public health emergency.
It has become increasingly clear that rising heat is having severe and widespread impacts on health and wellbeing. The link between heat and pregnancy is particularly severe — pregnant women and newborns are among those most vulnerable to these impacts.
We have previously shown how heat increases the risk of preterm birth, stillbirths, and low birth weight. We also describe impacts on congenital anomalies, and even some long-term effects of heat on unborn children.
In the latest update to our living review, we searched through all the published evidence produced by scientists across the world and synthesised this using narrative synthesis, vote counting and meta-analysis, which is a statistical approach to collate the findings of multiple studies.
The latest results bring together evidence from 198 studies across 66 countries, and 23 different outcomes, in the largest systematic review of its kind. This provides a comprehensive overview of how increasing temperatures can have serious health consequences for pregnant women and newborns.
The results are clear; heat is having significant and widespread impacts on pregnant women and newborns. Importantly, these effects are most profound in countries that are least responsible for the climate crisis and are the least able to adapt to its impacts.
Why Heat and Pregnancy Health Matters
Pregnancy is a time of significant physical strain, as any expectant mother will tell you. Rising temperatures add to the physical and emotional burden, placing significant strain on both the mother and the unborn baby.
The health of pregnant women and newborns has long been a marker of improving wellbeing in a population. Indeed, this is possibly one of the greatest achievements in public health.
Protecting the health of such a central part of a society has provided incredible return on investment. In fact, every single person reading this today owes their very existence to a successful pregnancy and newborn period.
Not everyone has been so fortunate, however. Poor birth outcomes, medical conditions in pregnancies, and other obstetric complications place a significant burden on individuals, populations, and health systems over a life course.
Key Findings: A Picture of Rising Risks
Our review uncovered significant associations between heat exposure and the following adverse outcomes:
- preterm birth
- stillbirth
- low birth weight
- hypertension and diabetes in pregnancy
- mental illness
- infections
- congenital anomalies
- obstetric complications
For example, we found that for every 1°C increase in temperature, the odds of preterm birth rose by 4%, and during heatwaves, the odds increased by 26%. When comparing these impacts between high-income and lower-income countries, we found a larger effect in lower-income countries, highlighting the unequal effects of climate change.
Rising temperatures were associated with a 28% higher risk of gestational diabetes and a nearly 50% increased risk of congenital anomalies.
These are not just percentages, but represent real increases in the number of adverse outcomes due to heat impacts on individual lives. When we’re dealing with effects this large, the numbers soon add up, with major social and economic impacts on society.
Rises in the burden of these illnesses threaten to undo decades of progress in protecting the health of pregnant women and their babies.
These findings matter for pregnant women and newborns worldwide, but particularly for those living in low- and middle-income countries and warmer climates. Here, pregnant women, already more vulnerable, may not be equipped to handle increases in heat. The healthcare systems, already under strain, are equally unprepared.
Despite these growing risks, climate change policies and communication have often overlooked maternal and neonatal health.
Why This Matters for Policymakers and Clinicians
By summarising and quantifying these risks, our study aims to support clinicians and policymakers in tracking the appropriate heat impacts and crafting targeted interventions for the most vulnerable. The findings suggest a need for early-warning systems, healthcare guidance for pregnant women during heatwaves, and adaptive measures in healthcare infrastructure. Clinicians should be prepared to address heat-related complications, especially in communities where heat is projected to worsen in the coming decades.
Beyond healthcare, policymakers must prioritise maternal and neonatal health in climate adaptation plans. Countries already facing high heat levels and those projected to face more extreme weather in the future must be prepared to address the unique risks that climate change poses to pregnant women and newborns.
Filling Knowledge Gaps for Global Impact
Our findings not only reveal significant risks around heat and pregnancy but also underscore glaring gaps in research. For example, while high-income countries have contributed most of the data on this topic, much less is known about the effects of heat on maternal health in low- and middle-income countries and tropical regions. With these areas expected to experience some of the most extreme impacts of climate change, filling this knowledge gap is essential for global health equity.
We are not powerless to prevent the worst impacts of climate change. Decisions we make today will have widespread and devastating impacts for generations to come. Let us not stand by and watch as pregnant women and children, especially those least responsible for the climate crisis, face the consequences of our inaction.
Our study is a call to action for healthcare providers, policymakers, and the public. As the climate crisis continues, the risks tied to heat and pregnancy will only grow for the world’s most vulnerable.
By addressing these health impacts head-on, we can build resilience in our healthcare systems and create a safer, more sustainable and more equitable future for mothers and their children.
Read the full study here: A systematic review and meta-analysis of heat exposure impacts on maternal, fetal and neonatal health