The influence of maternal smoking habits on the risk of subsequent stillbirth: is there a causal relation?

L Högberg,S Cnattingius

doi:10.1111/j.1471-0528.2007.01340.x

Abstract

ObjectiveMaternal smoking has previously been associated with risk of stillbirth. If women who quit smoking reduce their risk of stillbirth, the hypothesis of a causal association would be supported.DesignProspective cohort study.SettingNationwide study in Sweden.PopulationAll primiparous women who delivered their first and second consecutive single births between 1983 and 2001, giving a total number of 526 691 women.MethodA population-based Swedish study with data from the Medical Birth Registry, the Immigration Registry and the Education Registry. Logistic regression analyses were used to estimate odds ratios, using 95% confidence intervals.Main outcome measureStillbirth in the second pregnancy.ResultsCompared with nonsmokers in both pregnancies, women who smoked during the first pregnancy but not during the second do not have an increased risk of stillbirth (OR 1.02; 95% CI 0.79–1.30), while corresponding risk among women who smoked during both pregnancies was 1.35 (95% CI 1.15–1.58).ConclusionThe result supports that maternal smoking during pregnancy is causally associated with stillbirth risk. Smoking is a preventable cause of stillbirth, and smoking interventions is an important issue in antenatal care.

Highlights

Stillbirth is a relatively rare adverse pregnancy outcome in western countries such as Sweden (3.4 per 1000 live births1), but when it happens, it causes great emotional distress for the parents
A Canadian study found that stillbirth risk for women who had quit smoking by 16 weeks was higher than corresponding risk among nonsmokers and similar to that for women who smoked throughout pregnancy.[3]
When we adjusted for smoking in second pregnancy and other factors, smoking in first pregnancy was no longer associated with stillbirth risk in second pregnancy

Summary

Introduction

Stillbirth is a relatively rare adverse pregnancy outcome in western countries such as Sweden (3.4 per 1000 live births1), but when it happens, it causes great emotional distress for the parents. A lot of effort is devoted to investigate risk factors and causes of stillbirth. Smoking has repeatedly been associated with risk of stillbirth, and risks generally increase with the amount smoked. Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2.5, which does not permit commercial exploitation cessation, could be shown to reduce the risk of stillbirth. In a Danish cohort study, Wisborg et al.[2] found that risk of stillbirth to mothers who stopped smoking during the first trimester was comparable to the risk among women who were nonsmokers during the entire pregnancy. A Canadian study found that stillbirth risk for women who had quit smoking by 16 weeks was higher than corresponding risk among nonsmokers and similar to that for women who smoked throughout pregnancy.[3]

Methods

Results

Conclusion