Ambient temperature and stillbirth risks in northern Sweden, 1880-1950

Area of Science:

• Environmental Epidemiology
• Reproductive Health
• Historical Demography

Background:

• Unborn infant climate vulnerability is linked to adverse birth outcomes but remains poorly understood.
• Historical populations provide insights into environmental exposures and health.
• The impact of ambient temperature on stillbirth risk requires further investigation.

Purpose of the Study:

• To investigate the association between ambient temperature and stillbirth risk.
• To examine this association in a historical population in northern Sweden (1880-1950).

Main Methods:

• Utilized digitized parish records and daily temperature data from northern Sweden (1880-1950).
• Analyzed 141,880 births and 3,217 stillbirths using a time-stratified case-crossover design.
• Estimated incidence risk ratios (IRR) for lagged temperatures (0-7 days pre-birth), stratified by season and sex.

Main Results:

• Stillbirth risk elevated at both low (-10°C) and high temperatures during the extended summer (April-September) compared to +15°C.
• No significant temperature effect on stillbirth risk was observed during the extended winter (October-March).
• Male fetuses exhibited greater climate vulnerability than female fetuses.

Conclusions:

• Both extreme heat and cold during warmer months increased stillbirth risk in a pre-industrialization subarctic setting.
• Urbanization and socio-economic development may have influenced the decline in climate vulnerability.
• Findings highlight the historical impact of temperature extremes on fetal health.