Extreme Heat Linked to 5,515 Excess Preterm Births in Bangladesh

# Extreme Heat Linked to 5,515 Excess Preterm Births in Bangladesh

Human-induced climate change contributed to an estimated 1,479 additional preterm births in Bangladesh during the extreme heat event of April 2024, according to a new analysis by Zero Carbon Analytics (ZCA), an international research group focused on climate change and the energy transition.

The analysis estimates that these births would not have occurred during the month without the additional warming caused by human-induced climate change. The April 2024 heat event was made approximately 45 times more likely by climate change, according to World Weather Attribution.

A separate analysis by ZCA estimates that the heat event was associated with approximately 5,515 excess preterm births compared with a typical April during the 1991–2020 period.

This represents an 11.9% increase in preterm births, equivalent to about 19 additional cases per 1,000 births. Bangladesh recorded the highest rate among the three countries examined in the study.

The findings highlight the growing threat that climate-driven extreme heat poses to maternal and newborn health in Bangladesh, which already has one of the world's highest preterm birth rates.

Bangladesh's estimated preterm birth rate stood at 16.2% in 2020, the highest national average globally. South Asia recorded a regional rate of 13.2%.

Preterm birth, defined as birth before 37 completed weeks of pregnancy, is the leading cause of neonatal mortality worldwide. Babies born prematurely face an increased risk of death as well as long-term physical, neurodevelopmental and socioeconomic challenges.

## Dhaka and Chattogram account for nearly half of excess cases

The impact of extreme heat was not evenly distributed across Bangladesh, according to the analysis.

Dhaka and Chattogram, the country's two most populous divisions, together accounted for 47% of the estimated 5,515 excess preterm births associated with the April 2024 heat event.

Mymensingh emerged as another major area of concern. Temperatures there averaged 3.59 degrees Celsius above the division's typical April baseline, the largest increase among Bangladesh's divisions.

The estimated increase in preterm birth risk ranged from 10% to 15% across all divisions. Mymensingh recorded the highest rate of excess preterm births, at 24 per 1,000 births, despite ranking sixth among the country's eight divisions in the total number of additional cases.

Sylhet recorded the lowest rate, at 16 per 1,000 births.

The findings show why national averages alone cannot fully capture the health burden of extreme heat. More populous divisions may account for greater numbers of cases, while less populous areas can experience sharper increases in risk.

## An ordinary April could bring 1,500 excess cases by mid-century

The research warns that Bangladesh's heat-related preterm birth burden could increase further as global temperatures rise.

Under moderate and higher warming scenarios, ZCA projects that the country could experience approximately 1,500 excess preterm births during a typical April by mid-century, covering 2041–2060, compared with the 1985–2014 climate baseline.

The projected range is 630 to 2,900 cases, alongside an estimated 1.1-degree Celsius rise in April temperatures by mid-century.

Dhaka Division is expected to face the largest burden, followed by Chattogram and Rajshahi.

The projections assume that no additional adaptation measures are introduced and that the relationship between temperature and preterm birth risk remains consistent with current evidence. They also account for projected changes in the number of births.

## Heat protection needs to become part of maternal healthcare

Pregnant women are particularly vulnerable to extreme heat because of the physiological demands of pregnancy. Heat exposure can contribute to dehydration, reduced blood flow to the placenta, inflammation and the activation of biological pathways that may trigger labour.

Dr Ummay Hafsa Mazumde, a medical officer at Cumilla Sadar South Health Complex, said intense heat could pose serious risks to pregnant women.

Excessive sweating can cause substantial electrolyte loss, potentially leading to serious health complications for both mothers and their unborn children, she said.

The risks can be compounded by poverty, nutritional anaemia, strenuous physical work, limited access to antenatal care and inadequate cooling facilities. Poorly ventilated homes and building materials that trap heat can also increase exposure, even when women remain indoors.

Bangladesh took a step towards addressing these risks in 2024, when the Directorate General of Health Services, in collaboration with UNICEF, introduced national guidelines aimed at protecting children and pregnant women from heat stress. The guidelines recognised the risks associated with heat exposure, including preterm birth.

However, heat protection has yet to be systematically integrated into routine maternal healthcare programmes. The challenge is to translate existing guidance into practical protection for pregnant women and newborns, particularly in communities facing the greatest exposure.

Potential measures include incorporating heat-risk information into antenatal care, strengthening community-based maternal health services, improving access to cooling and hydration, and expanding heat early-warning systems.

The research also highlights the need to strengthen healthcare preparedness in divisions with the largest estimated burden while ensuring that areas experiencing the sharpest increases in risk are not overlooked.

Dr Joanne Bentley-McKune, lead author of the report and a senior research analyst at ZCA, said climate change was making extreme heat more frequent and intense, increasing the risk of preterm birth and potentially lifelong health consequences.

She noted that Bangladesh had contributed relatively little to the historical emissions driving climate change but remained disproportionately affected by climate-related extreme weather, despite having fewer resources for adaptation than many high-income, high-emitting countries.

The estimates could help identify areas where greater healthcare capacity was needed, she said, adding that improved antenatal care and early-warning systems should be prioritised. However, adaptation measures alone would prevent only some of the additional preterm births associated with climate change, making it crucial to limit further global warming.

Prof Dr Iqbal Kabir, a climate and public health expert and director of the Center for Climate Change and Public Health, described the findings as a wake-up call for Bangladesh.

He said the estimated 5,515 excess preterm births during the April 2024 heat event underscored the need to integrate heat protection into maternal healthcare.

He called for stronger heat-risk screening and counselling during antenatal visits, better support for frontline health workers, improved early-warning systems and access to safe, cool environments, particularly for vulnerable communities.

Protecting mothers and newborns from extreme heat, he said, requires coordinated action across the healthcare system, climate policy and communities.