['There has been a world-wide increase in the incidence of ectopic pregnancies over the last decades. In Norway about 1,500 women are hospitalized every year because of this potentially lethal condition. Several studies have shown that smoking is one of several risk factors for ectopic pregnancies. We wanted to examine whether such an association could be established in a large Norwegian material.', 'We analysed data from a cross-sectional questionnaire-based study of 9,237 Norwegian women aged 35-49 years. 61.6% responded.', '67.4% of the women were present or previous smokers. 301 (3.3%) had experienced an ectopic pregnancy. We found that smokers had a relative risk of 1.5 (95% CI 1.1-1.9) for ectopic pregnancy compared to non-smokers.'] Is [ Smoking associated with increased risk of ectopic pregnancy -- a population based study ]?