Countries should watch for spikes in preterm births, stillbirths and child deaths during heatwaves, four UN agencies said on Wednesday, launching what they called the first global set of indicators to help governments track the health toll of extreme heat on mothers and newborns.
The 19 indicators from the World Health Organization (WHO), the World Meteorological Organization (WMO), UNICEF and the UN Population Fund (UNFPA) range from preterm births and clinic visits to air temperature readings and whether health ministries include mothers and children on their climate task forces.
Matched with weather data, routine hospital and clinic records can help health officials prepare for patient surges, sharpen warnings to pregnant women and pinpoint the communities most at risk, the agencies said. Over time, they should also reveal how heat harms mothers and babies as heatwaves grow longer, more frequent and more severe.
“Heat is already affecting our most vulnerable populations, including pregnant women, newborns and children,” said Dr Pascale Allotey, director of WHO’s Department of Sexual, Reproductive, Maternal, Child and Adolescent Health and Ageing. “But what health systems do not count, they cannot respond to.”
“By tracking outcomes such as preterm birth, child deaths and illnesses, and health-facility visits alongside heat exposure, countries can identify potential impacts and take action to protect women and children,” Allotey added.
An estimated 1.5 billion children are exposed to heatwaves that are becoming more frequent, longer or more severe, according to the agencies. Babies under one experienced 389% more heatwave days per person in 2024 than the 1986–2005 average, according to the Lancet Countdown.
Heatwaves raise the odds of preterm birth by 26%, a 2024 meta-analysis of 198 studies across 66 countries found. Complications of preterm birth are the leading cause of death in children under five, according to WHO.
“Many countries lack practical guidance on which health indicators to track, how to interpret trends alongside heat exposure data, and how to integrate these considerations into routine monitoring systems,” senior officials from WHO, WMO, UNICEF and UNFPA wrote in a joint foreword to the report.
The indicators are not meant to prove cause and effect, but offer “a practical starting point for identifying trends, signalling potential impacts, and informing action,” the officials said.
“What remains constant, however, is the need to ensure that women, newborns and children are visible in climate and health monitoring efforts and that their needs are reflected in policies and programmes,” they wrote.
Mothers and newborns missing from heat plans
Research on extreme heat’s effects on pregnancy and newborn health has expanded quickly in recent years, yet monitoring has lagged because of uncertainty over which outcomes heat affects most, the agencies’ joint report says.
A 2025 WHO-commissioned review of 83 heat-health action plans from 24 countries found only 52% named pregnant women as an at-risk group, while 39% named newborns and 14% postpartum or breastfeeding women. None comprehensively addressed the risks to mothers and children during extreme heat, and monitoring mechanisms were inadequate to assess heat’s impact on them.
The review also found no plans from low-income countries, where a woman faces a 1 in 66 lifetime risk of dying from a maternal cause, compared with 1 in 7,933 in high-income countries, according to WHO data.
Only 3% of studies on heat and pregnancy come from low-income countries, compared with 63% from high-income countries and temperate climates, according to the International Confederation of Midwives (ICM), which took part in talks that shaped the indicators.
ICM also cites a WHO survey of member states that found 80% of countries mention heat in their national health adaptation plans, but only 30% include concrete actions and just 2% explicitly mention actions for mothers, newborns and children.
“As our world continues to heat up, it creates new risks for health, and older people, pregnant women, newborns and children are among those least able to escape them,” said Bruce Gordon, acting director of WHO’s Department of Environment, Climate Change, One Health and Migration. “Our health systems need the data to recognise this reality and take action.”
What countries are asked to track
Preterm births and outpatient visits form the core of routine monitoring. Both are read against air temperature, the baseline heat measure recommended for every country. Measures that also factor in humidity, such as the heat index and wet-bulb globe temperature, are optional.
Countries are also urged to watch for hypertension in pregnancy, late stillbirths, low birthweight and under-five deaths in facilities, and to break down deaths and emergency visits during heat events by age and sex, while tracking school attendance can show how heat disrupts children’s lives, the agencies said.
Six more indicators in the report test whether governments are following through with policy and monitoring. They include whether vulnerability assessments treat women and children as distinct at-risk groups and what share of local health authorities receive heat early warnings.
WHO also urged all countries to develop heat-health action plans that meet the needs of pregnant women, newborns and children, strengthen early warning systems and trigger timely action when heat risks emerge.
“Measurement drives action,” the officials wrote in their foreword. “By strengthening our ability to monitor the impacts of heat on maternal, newborn and child health, we can better protect those at greatest risk.”
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