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Season and outdoor ambient temperature: effects on birth weight
L J Murray1, D P O'Reilly, N Betts
1Department of Epidemiology and Public Health, The Queens University of Belfast, Belfast, United Kingdom. l.murray@qub.ac.uk
Obstetrics and Gynecology
|October 24, 2000
Summary
Seasonal variations in birth weight show that infants born in late spring and summer are lighter. This pattern is linked to meteorological factors, particularly temperature during mid-pregnancy.
Area of Science:
- Environmental Health
- Perinatal Epidemiology
- Human Reproduction
Background:
- Birth weight seasonality is a recognized phenomenon.
- The influence of meteorological factors on birth weight requires further elucidation.
Purpose of the Study:
- To quantify the impact of meteorological variables on seasonal birth weight patterns in a developed country.
- To identify specific environmental exposures during pregnancy linked to birth weight variations.
Main Methods:
- Utilized birth weight data for singleton live births (1971-1986) in Northern Ireland.
- Correlated birth weights with daily temperature, rainfall, and sunshine data.
- Employed linear regression models, adjusting for multiple covariates including gestational age and maternal factors.
Main Results:
- Observed a distinct seasonal pattern, with lowest birth weights in May, June, and July.
- Mean birth weights were significantly lower in summer months compared to January.
- The seasonal effect in female infants was largely explained by mean daily maximum temperature during the second trimester.
Conclusions:
- Lower birth weights in late spring/summer may be attributed to exposure to lower winter temperatures during mid-gestation.
- Maternal exposure to cold during mid-pregnancy could be a key factor influencing fetal growth.
- Recommendations for pregnant women to maintain warmth during mid-pregnancy are suggested to mitigate potential adverse effects on birth weight.