The effect of a major earthquake experienced during the first trimester of pregnancy on the risk of preterm birth

Background On 22 February 2011 an earthquake (magnitude 6.3) hit Christchurch, New Zealand. Earthquakes have been associated with increased risks of preterm birth (PTB) and other adverse pregnancy outcomes. However, the literature on this subject is scarce. Maternal antenatal stress has been suggested as the link between earthquakes and PTB. In this study the Christchurch earthquake was utilised as a model of maternal stress to assess its effects on PTB rates and other pregnancy outcomes. Aim To investigate whether women who experienced a major earthquake during the first trimester of pregnancy were at an altered risk of PTB compared to women who did not experience an earthquake during their pregnancy. Methods This was a retrospective cohort study. Women carrying a singleton pregnancy in their first trimester on 22 February, 2011 were identified for a post-earthquake cohort (n = 1057). A group of women pregnant in 2009 were identified for a pre-earthquake cohort (n = 1314). Data were obtained from electronic medical records and the hospital clinical coding database. Chi-square test, Fisher's exact test and Wilcoxon rank sum test were used to analyse differences in pregnancy outcomes. Statistically significant variables together with earthquake exposure were assessed as risk factors for PTB using a multivariate logistic regression model. Results No significant difference in the rate of PTB was found between the two groups P > 0.05). Conclusion Women carrying a singleton pregnancy in this study who experienced a major earthquake in their first trimester do not seem to be at an increased risk of PTB.