In Europe, about 6%–8% of women smoke during pregnancy. Smoking has numerous harmful effects on fetal growth and pregnancy outcomes and is the most preventable cause of pregnancy complications. This dissertation studies the association between smoking and maternal health during pregnancy and smoking in consecutive pregnancies.

This dissertation utilized data from two Finnish registers. The smoking data were retrieved from the Medical Birth Register and was connected to data concerning specialized care during pregnancy from the Finnish Care Register for Health Care. The first study examined the association between smoking and specialized care due to different ICD-10 diagnoses (in chapters) among pregnant women in Finland from 1999 to 2015 (n = 936,113). The second study investigated the relationship between smoking and urinary tract infections among pregnant women from 2006 to 2018 in Finland (n = 723,433). In the third study, the connection between prior psychiatric specialized care and smoking during the second pregnancy was studied among women who had smoked during their first pregnancy and had two deliveries from 2006 to 2019 (n = 29,683). These associations were studied using logistic regression analysis and adjusted for several confounding factors, e.g., year of delivery, maternal age, parity, and marital status.

The smoking prevalence in these studies was 14.5%–16.0%. According to our findings, women who smoke during pregnancy are more likely to receive specialized care during pregnancy than women who do not smoke. This association is even more pronounced in women who continue smoking after the first trimester. Smoking appears to be linked to an increased likelihood of urinary tract infections. Lifetime psychiatric morbidity was associated with smoking during the second pregnancy, compared to women without a previous psychiatric diagnosis, among women who smoked during their first pregnancy.

These results strengthen the knowledge that, in addition to harmful effects on the fetus and pregnancy, smoking also impairs maternal health during pregnancy. Smoking cessation support is still needed before, during, and after pregnancy. Smoking cessation support should be more precisely tailored, with particular consideration given to the mother’s prior mental health history.