Panjim, Goa: Climate change has contributed to around 8,830 additional preterm births in India during the exceptionally hot April of 2024, with Bihar, Uttar Pradesh, West Bengal and Jharkhand bearing the largest share of the burden, according to a new analysis by Zero Carbon Analytics (ZCA).The analysis estimates that around 8,830 preterm births in India during the month were attributable specifically to the additional warming caused by human activity. Across India, Bangladesh and the Philippines, the figure was approximately 10,600.The findings come against the backdrop of another year of unprecedented heatwaves and other extreme weather fuelled by climate change, with global heating also supercharging the current El Nino.Researchers found that the April 2024 heatwave was associated with around 16,150 more preterm births across the three countries compared with what would have been expected during a typical April. India accounted for a 3.6% increase compared with 11.9% in Bangladesh and 10% in the Philippines. India recorded approximately 10,050 of these excess births compared with a typical April between 1991 and 2020.The two figures measure different things. The estimate of 10,050 measures how many more preterm births occurred in India in April 2024 than would be expected in a typical April. The figure of 8,830 estimates how many preterm births would not have occurred if human-caused climate change had not added to the heat during that month.Human-caused climate change made the April 2024 heat event around 45 times more likely in South Asia according to the analysis, which draws on temperature records, preterm birth data and climate attribution research.Heatwaves increase the risk of preterm birthsWorld Health Organisation (WHO) defines preterm birth as the birth of a baby before 37 completed weeks of pregnancy. As per an analysis published by The Lancet, it is the leading cause of death among newborns globally and can have long-term physical, neurodevelopmental and socioeconomic consequences for children.The analysis mentions that exposure to high temperatures, even for a few days, can increase the odds of a preterm birth. A synthesis of global studies cited in the report found that a 1°C increase in heat exposure is associated with 4% higher odds of preterm birth. During heatwaves, the odds increase by 26%.Also read: India’s Climate Crisis is Killing, Sickening and Costing People Their Livelihoods: Lancet CountdownSeveral biological processes may explain the link, including dehydration, reduced blood flow to the placenta, inflammation and the activation of pathways that can trigger labour. However, the precise contribution of these mechanisms is not yet fully understood, and the effects can vary depending on the stage of pregnancy and the duration of heat exposure.Pregnant women are particularly vulnerable to extreme heat because of the physiological demands of pregnancy. The risks can be compounded by poor nutrition, anaemia, strenuous physical work and inadequate access to healthcare.Women living in poverty may face additional challenges, including long hours of outdoor work and homes that trap heat, often without reliable electricity or affordable cooling.In a statement, Dr Rashmi Agarwalla, nodal officer for climate change and associate professor in the Department of Community and Family Medicine at AIIMS Guwahati, said pregnant women and newborns were particularly vulnerable in climate-affected countries such as India.“Anaemia, poor nutrition, and prolonged outdoor work further compound these risks, particularly in vulnerable communities. Yet, heat remains an often-overlooked threat to maternal and neonatal health within our healthcare systems,” she said.Four states bear 65% of India’s heatwave burdenThe analysis found that the impact of the April 2024 heat event was not evenly distributed across India. Bihar, Uttar Pradesh, West Bengal and Jharkhand together accounted for around 65% of the country’s estimated excess preterm births.Nationally, the average temperature in April 2024 was 0.94°C above the usual level. However, there were significant differences between states. Nine states experienced cooler than usual conditions, while Tripura and Mizoram were around 2.7°C warmer than their April averages.In these two northeastern states, the increase in heat was associated with an estimated 11% rise in preterm birth risk.The analysis also found that the number of excess preterm births did not always correspond directly with the intensity of the heat. Population size and the existing prevalence of preterm births also influenced the overall burden.Also read: Heatwave Intensity, Frequency and Hotspot Extent Have Increased in India Over the Last 26 Years: StudyFor instance, Uttar Pradesh recorded a relatively smaller increase in preterm birth risk of around 3%, as April temperatures were 0.74°C above normal. However, its large population meant that even this small rise led to a substantial number of additional preterm births.Bihar and West Bengal had both large populations and higher increases in preterm birth risk. The risk rose by 10% in West Bengal and 7% in Bihar.Karnataka had the highest rate of excess preterm births among the states, with 12 additional births for every 1,000 births. This was linked to temperatures being around 2°C above normal and the state already having a higher-than-average rate of preterm births. Mizoram, despite one of the largest rises in preterm birth risk, had one of the lowest rates per 1,000 births, because preterm birth there is less common.An ordinary April in 2050 could be worse than the 2024 heatwaveThe analysis also warns that the burden of heat-related preterm births is likely to increase as temperatures continue to rise.India is projected to experience more than 15,000 excess preterm births during a typical April by the middle of the century. This means that an ordinary April around 2050 could result in more excess preterm births than the unusually hot April of 2024.Uttar Pradesh is projected to record the highest number of excess preterm births in absolute terms, followed by Bihar and Rajasthan.Also read: Hot Nights are Making India’s Heatwaves WorseThe findings are particularly concerning given India’s already high preterm birth rate. According to the analysis, India’s rate stood at 13% in 2020. The country accounted for around 20% of all preterm births globally that year.Maternal healthcare systems are not preparedAlthough a lot of evidence shows that extreme heat can put pregnant women and their babies at risk, the analysis finds that health programmes and heat action plans in India, Bangladesh and the Philippines still do not adequately protect them.India and Bangladesh have recently issued pregnancy-specific heat guidance, but protection from extreme heat is not yet a routine part of maternal healthcare.The report calls for heat protection to be integrated into antenatal care (medical care and check-ups a woman receives during pregnancy to protect her health and the baby), community-based maternal health services and broader health-system preparedness. It also recommends improving access to cooling facilities and early warning systems, particularly in communities identified as vulnerable.Agarwalla also called for maternal heat protection to become a routine part of healthcare planning, warning that existing health systems were not adequately equipped to address the risks.