Biological Impacts of Rising Temperatures on Maternal, Fetal, and Newborn Health: BIRTH Cohort
Biological Impacts of Rising Temperatures on Maternal, Fetal, and Newborn Health: A Cohort Study (BIRTH Cohort)
About the Project
Climate change is increasing the frequency and intensity of extreme heat events, with disproportionate effects on vulnerable populations, particularly women and children in low-resource settings. Pakistan is among the countries most affected by climate-related heat exposure, with prolonged heatwaves, rising temperatures, water scarcity, food insecurity, and displacement creating additional pressures on communities.
Pregnancy is a period of heightened sensitivity to environmental stress. Evidence links heat exposure with adverse pregnancy and birth outcomes, including pre-eclampsia, gestational diabetes, preterm birth, low birth weight, stillbirth, and fetal growth restriction. However, there remains limited evidence on the biological pathways through which heat affects pregnant women, fetal development, and newborn health, particularly in low- and middle-income country settings.
The BIRTH Cohort is a large-scale prospective cohort study in Pakistan that follows pregnant women from early pregnancy through delivery and into the first year after birth. The study combines individual-level heat exposure monitoring, wearable sensors, ultrasound assessments, biological samples, and clinical follow-up to understand how extreme heat affects maternal, fetal, and newborn health.
By generating evidence from rural and peri-urban areas of Sindh, the study aims to support climate-resilient maternal and newborn health strategies in Pakistan and other settings facing increasing heat stress.
Project Objectives
- Assess the acute and sustained effects of environmental heat exposure on pregnancy and birth outcomes in rural and peri-urban areas of Pakistan.
- Examine the bio-physiological pathways through which heat stress affects maternal, fetal, and infant health across different stages of pregnancy.
- Evaluate how gestational age, socio-demographic factors, maternal health, and nutritional status modify the relationship between heat exposure and adverse pregnancy outcomes.
- Generate evidence to support climate-resilient maternal and newborn health policies and interventions.
Methodology / Approach
BIRTH is a prospective cohort study that follows pregnant women from early pregnancy through delivery and for 12 months after birth. The study will enroll 6,000 pregnant women before 14 weeks of gestation, with a sub-cohort of 1,000 women participating in more intensive physiological monitoring using wearable devices.
Participants attend scheduled visits at enrollment, 18–22 weeks, 28–32 weeks, 36–37 weeks, and within 48 hours of birth, followed by quarterly visits until 12 months after delivery. These visits include demographic and obstetric information, anthropometric measurements, dietary recalls, clinical assessments, and serial fetal ultrasound, Doppler, and echocardiography.
To measure heat exposure, participants wear ambient temperature and humidity loggers throughout the study. Women in the sub-cohort also wear a Fitbit smartwatch and a skin-temperature sensor to capture physiological responses to heat in real time. Biological samples are collected to examine inflammatory and stress-related pathways linked to heat exposure.
The study’s primary outcomes include low birth weight and small vulnerable newborns. Secondary outcomes include preterm birth, miscarriage, stillbirth, fetal growth restriction, and maternal complications such as gestational hypertension and gestational diabetes. Statistical modelling will be used to assess the relationship between heat exposure and pregnancy outcomes, including cumulative and delayed effects across pregnancy.
Study Location
Pakistan
The study is being implemented in Matiari, Tando Muhammad Khan, and Tharparkar/Mithi districts of Sindh, covering rural and peri-urban communities.
Study Population
The project focuses on pregnant women and infants in rural and peri-urban areas of Sindh, Pakistan. Pregnant women are enrolled during the first trimester and followed throughout pregnancy, delivery, and the first 12 months after birth.
The study is expected to benefit women, newborns, families, local communities, healthcare providers, researchers, policymakers, and public health planners by generating evidence on how extreme heat affects maternal, fetal, and newborn health. The findings will support the development of climate-resilient maternal and child health strategies for vulnerable populations.
Project Team
Principal Investigator
Dr Jai K. Das Associate Director, Institute for Global Health and Development
Associate Professor, Department of Paediatrics and Child Health
Aga Khan University, Karachi, Pakistan
Co-Investigator
Dr Lumaan Sheikh Chair and Professor, Department of Obstetrics and Gynaecology
Aga Khan University, Karachi, Pakistan
Co-Investigator
Dr Zainab Samad Professor and Chair, Department of Medicine
Aga Khan University, Karachi, Pakistan
Co-Investigator
Dr Zulfiqar A. Bhutta Institute for Global Health and Development, Aga Khan University, Pakistan
Centre for Global Child Health, The Hospital for Sick Children, Toronto, Canada
Co-Investigator
Dr Aris T. Papageorghiou Nuffield Department of Women’s & Reproductive Health
University of Oxford, United Kingdom
Co-Investigator
Dr Nadeem F. Zuberi Department of Obstetrics and Gynaecology / Feto-Maternal Unit
Aga Khan University, Pakistan
Co-Investigator
Dr Nuruddin Mohammed Department of Obstetrics and Gynaecology / Feto-Maternal Unit
Aga Khan University, Pakistan
Co-Investigator
Dr Zaheena Islam Department of Obstetrics and Gynaecology / Feto-Maternal Unit
Aga Khan University, Pakistan
Co-Investigator
Dr Saqib Hamid Qazi Department of Surgery (Paediatric Surgery)
Aga Khan University, Pakistan
Project Management and Coordination
Dr Suneel Piryani
Dr Mahnaz Ambareen
Dr Asma Abdul Malik
Other Key Team Members
Dr Harshana Kumari
Ms Qumber Ali
Ms Sana Khatoon
Research Partners
Department of Paediatrics and Child Health Aga Khan University
Department of Obstetrics and Gynaecology Aga Khan University
Nutrition Research Laboratory Aga Khan University
Section of Paediatric Cardiology Sindh Institute of Urology and Transplantation (SIUT)
Oxford Maternal and Perinatal Health Institute University of Oxford
Centre for Global Child Health The Hospital for Sick Children, Toronto
London School of Hygiene and Tropical Medicine
Supported By
Wellcome Trust
Grant Status
Active / Ongoing
Key Achievements
- Field implementation began on April 7, 2025.
- Participant recruitment is ongoing, with 2,077 pregnant women enrolled out of a target of 6,000.
- Approximately 670 women have completed pregnancy and delivery, with follow-up assessments in progress to measure child health outcomes.
- The study protocol has been published in BMJ Open.
- Regular staff trainings are being conducted on standard operating procedures, data tools, participant follow-up, and quality assurance.
Expected Outputs / Deliverables
- Research publications on heat exposure, pregnancy outcomes, fetal development, and newborn health.
- Stakeholder and policy engagement to inform climate-resilient maternal health strategies.
- Community dissemination sessions with participants and local healthcare providers.
- Evidence to support climate adaptation planning for maternal, fetal, and newborn health in Pakistan and other low- and middle-income countries.
Reports and Resources
Why This Matters
The BIRTH Cohort Study will generate large-scale evidence from Pakistan on how extreme heat affects pregnant women, fetal development, and newborn health. By combining individual-level heat exposure monitoring with advanced ultrasound assessments and biological sampling, the study will provide new insights into how rising temperatures influence pregnancy and birth outcomes.
The findings will help identify critical periods of vulnerability during pregnancy, improve understanding of the biological pathways through which heat affects maternal and fetal health, and support the development of climate-resilient health interventions.
The evidence generated will inform maternal and child health policy, strengthen climate adaptation planning, and contribute to protecting vulnerable populations in Pakistan and other low- and middle-income countries facing increasing heat stress due to climate change.
Keywords
Climate Change; Heat Stress; Pregnancy; Birth Outcomes; Cohort Study; Maternal Health; Pakistan; Fetal Growth; Climate Resilience; Newborn Health
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