Extreme heat caused an estimated 5,515 additional premature births in Bangladesh in April 2024 compared with a typical April, according to a new analysis by international research organisation Zero Carbon Analytics (ZCA).

The number represents an 11.9% increase over premature births recorded during previous Aprils with normal temperatures.

The study, published on Monday, found that human-induced climate change was directly responsible for the additional heat that contributed to 1,479 of these premature births.

Climate change made the extreme heatwave in April 2024 around 45 times more likely, the analysis found.

Researchers estimated that extreme heat caused approximately 19 additional premature births for every 1,000 deliveries in Bangladesh during the heatwave. Among the three countries covered by the study — Bangladesh, India and the Philippines — Bangladesh recorded the highest rate.

According to 2020 statistics, Bangladesh also had the world’s highest national rate of premature births, at 16.2%, compared with the South Asian regional average of 13.2%.

A baby born before completing 37 weeks of pregnancy is classified as premature or preterm. Premature birth is one of the leading causes of newborn deaths worldwide and is associated with an increased risk of long-term physical and neurological developmental complications.

Dhaka and Chattogram account for 47% of additional cases

The impact of extreme heat was not evenly distributed across the country. Nearly 47% of the 5,515 additional premature births linked to the April 2024 heatwave were recorded in Dhaka and Chattogram divisions.

However, Mymensingh experienced the highest temperature anomaly, with average temperatures in April rising 3.59 degrees Celsius above normal — the largest increase among the country’s eight divisions.

Although Mymensingh ranked sixth in terms of the total number of additional premature births, it recorded the highest rate, at 24 additional premature births per 1,000 deliveries.

Sylhet recorded the lowest rate, with 16 additional premature births per 1,000 deliveries.

The risk of premature births increased by 10% to 15% across all divisions, highlighting the widespread impact of extreme temperatures on maternal health.

Risk could increase further by mid-century

The study warned that rising global temperatures could lead to more heat-related premature births in the coming decades.

Compared with the 1985–2014 climate baseline, Bangladesh could see an average of around 1,500 additional premature births during a typical April each year by mid-century (2041–2060), according to the projections.

The estimated range is between 630 and 2,900 additional cases.

Average April temperatures are projected to rise by around 1.1 degrees Celsius during this period, with Dhaka division expected to face the greatest impact, followed by Chattogram and Rajshahi.

The projections assume no new adaptation measures are introduced and that the relationship between temperature and premature birth risk remains unchanged.

Dr Umme Hafsa Majumder, medical officer at Cumilla Sadar South Upazila Health Complex, said extreme heat poses serious health risks to pregnant women.

“Extreme heat creates serious health risks for pregnant women. Excessive sweating causes the body to lose substantial amounts of electrolytes, which can lead to serious complications for both the mother and the unborn child,” she said.

She explained that exposure to excessive heat during pregnancy can cause dehydration, reduce blood flow to the placenta, trigger inflammation and activate biological responses that may induce labour prematurely.

Majumder added that poverty, anaemia caused by malnutrition, excessive physical labour, inadequate antenatal care and a lack of facilities to keep homes cool can further intensify these risks.

Pregnant women can remain vulnerable to extreme heat even indoors, particularly in homes with inadequate ventilation, she said.