Department of Social and Environmental Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
PLoS One. 2012;7(7):e40228. doi: 10.1371/journal.pone.0040228. Epub 2012 Jul 6.
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.
大多数地区都描述了低出生体重 (LBW) 和早产 (PTB) 的季节性，有证据表明这种模式是由环境室外温度引起的。然而，这种关联、影响的方向和暴露的关键时间仍然存在争议。
对数逻辑、时间序列回归分析了来自德国两个州的近 30 万例分娩，以研究季节与每日平均温度之间的关系，以及足月 LBW（tLBW）或 PTB 的日比例变化。分析调整了随时间变化的因素。在妊娠的不同时期检查了温度暴露情况。
对于受孕季节、出生季节或环境室外温度与 tLBW 或 PTB 之间的关联，只有微弱的证据。两个州之间的温度分析结果不一致。检测到并描述了不同的偏倚来源，这些偏倚可能会人为地导致更强的发现。
没有发现受孕季节、出生季节或温度与 tLBW 或 PTB 之间存在明确的关联。在妊娠结局的研究中，可以确定不同的偏倚来源，这些来源可能可以解释过去存在的异质性发现。
