Extreme temperature and preterm birth: Time windows and geographical disparities

Area of Science:

• Environmental Health
• Reproductive Epidemiology
• Climate Change Impacts

Background:

• Preterm birth (PTB) remains a leading cause of neonatal mortality and morbidity worldwide.
• Maternal exposure to extreme temperatures is increasingly recognized as a potential environmental risk factor for adverse pregnancy outcomes.
• Understanding the specific timing and magnitude of temperature exposure effects on PTB is crucial for public health interventions.

Purpose of the Study:

• To systematically evaluate the association between prenatal exposure to heat and cold and the risk of preterm birth (PTB).
• To investigate how different time windows of temperature exposure influence PTB risk.
• To identify specific climatic or demographic factors that may modify these associations.

Main Methods:

• A comprehensive systematic literature search was conducted across Embase, Web of Science, PubMed, and Scopus.
• Data from 32 eligible studies were extracted, focusing on temperature exposure timing, temperature levels, and PTB prevalence.
• Six random-effects meta-analyses were performed, stratified by temperature percentile and exposure time windows, adhering to PRISMA guidelines.

Main Results:

• High temperatures within one week before delivery significantly elevated PTB risk (RR=1.05), with higher risks observed in subtropical regions and developing countries.
• Positive associations between high temperatures and PTB were found for exposure windows of 1-4 weeks (RR=1.07) and beyond four weeks (RR=1.20) prior to delivery.
• Cold exposure showed a significant association with increased PTB risk only when occurring more than four weeks before delivery (RR=1.21).

Conclusions:

• Prenatal exposure to high temperatures is a significant risk factor for preterm birth, particularly in early pregnancy and subtropical climates.
• The impact of cold exposure on PTB risk is less clear but warrants further investigation, especially for prolonged exposures.
• These findings underscore the need for climate-resilient prenatal care strategies, including heat warnings and cooling measures, to mitigate climate change's health impacts on mothers and infants.