The association of season and temperature with adverse pregnancy outcome in two German states, a time-series analysis

A seasonality of low birth weight (LBW) and preterm birth (PTB) has been described for most regions and there is evidence that this pattern is caused by ambient outdoor temperature. However, the association as such, the direction of effect and the critical time of exposure remain controversial. Logi...

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Bibliographic Details
Published in:PloS one 2012-07, Vol.7 (7), p.e40228
Main Authors: Wolf, Jennyfer, Armstrong, Ben
Format: Article
Language:English
Subjects:
20th century
Age
Air pollution
Analysis
Bias
Biology
Birth weight
Childbirth & labor
Environmental health
Epidemiology
Exposure
Female
Germany - epidemiology
Heat
Humans
Humidity
Hygiene
Hypotheses
Infant, Low Birth Weight
Infant, Newborn
Infectious diseases
Low birth weight
Male
Mean daily temperatures
Mean temperatures
Medicine
Menstruation
Mortality
Outdoor air quality
Preeclampsia
Pregnancy
Pregnancy Outcome - epidemiology
Pregnant women
Premature Birth
Premature infants
Public health
Regression analysis
Seasonal variations
Seasons
Statistical methods
Studies
Temperature
Temperature effects
Time series
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Summary:A seasonality of low birth weight (LBW) and preterm birth (PTB) has been described for most regions and there is evidence that this pattern is caused by ambient outdoor temperature. However, the association as such, the direction of effect and the critical time of exposure remain controversial. Logistic, time-series regression was performed on nearly 300,000 births from two German states to study the association between season and daily mean temperature and changes in daily proportions of term LBW (tLBW) or PTB. Analyses were adjusted for time-varying factors. Temperature exposures were examined during different periods of pregnancy. Weak evidence for an association between season of conception, season of birth or ambient outdoor temperature and tLBW or PTB was found. Results of analyses of temperature were not consistent between the two states. Different sources of bias which would have artificially led to stronger findings were detected and are described. No clear evidence for an association between season of conception, season of birth or temperature and tLBW or PTB was found. In the study of pregnancy outcome different sources of bias can be identified which can potentially explain heterogeneous findings of the past.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0040228