Lifetime psychiatric morbidity and maternal smoking behavior in consecutive pregnancies: A Finnish register study.

Introduction: Despite the adverse effects of smoking during pregnancy, a large proportion of women who smoke during their first pregnancy endure smoking also in their subsequent one. Previous studies have made efforts to explore associated factors, such as maternal mood and stress. This observational register-based historical cohort study aims to investigate the association between prior psychiatric morbidity and maternal smoking during consecutive pregnancies.

Material and methods: The study population comprised all women who smoked during their first pregnancy and had two singleton live births between January 1, 2006 and December 31, 2019 in Finland (n = 29 683). The smoking information was obtained from the Finnish Medical Birth Register, categorized as "no smoking," "quit smoking" (during the first trimester), or "continued smoking" (beyond the first trimester). Maternal psychiatric diagnoses (from the age of 15 until the second delivery) were derived from the Finnish Hospital Discharge Register. The association between (I) any psychiatric diagnosis, (II) separate diagnosis groups, and (III) psychiatric burden (diagnoses from 0 to 5 different diagnosis groups) and maternal smoking during the second pregnancy was analyzed using logistic regression.

Results: The smoking prevalence during the first pregnancy was 16.0%. Women who continued smoking during their first pregnancy (n = 15 588) were likely smokers in their second: 54.9% continued, and 12.4% quit smoking. Most women who quit smoking during their first pregnancy (n = 14 095) were non-smokers during their second (73.2%). Women who continued smoking during their first pregnancy and had any previous psychiatric diagnosis were more likely to continue smoking (beyond the first trimester) during their second pregnancy (OR 1.44, 95% CI 1.32-1.57) compared to those without such a diagnosis. A similar association was found between psychiatric burden and continued smoking (OR 1.20, 1.14-1.25). Women who quit smoking during their first pregnancy and had any diagnosis or burden showed a similar trend for continued smoking but were not more likely to quit smoking during the second pregnancy.

Conclusions: Any prior psychiatric diagnosis seems to be associated with continued smoking during the second pregnancy among first-pregnancy smokers. Psychiatric and smoking cessation support should be targeted particularly to women who smoke during their first pregnancy and have psychiatric conditions in their medical history.