The aim of our study was to assess associations between smoking behavior before and
during pregnancy and selected adverse birth outcomes. This study is based on the Murmansk
County Birth Registry (MCBR). Our study includes women who delivered a singleton pregnancy
after 37 weeks of gestation (N = 44,486). Smoking information was self-reported and assessed at the
first antenatal visit during pregnancy. We adjusted for potential confounders using logistic regression.
The highest proportion of infants with low values of birth weight, birth length, head circumference,
ponderal index and of the Apgar score at 5 min was observed for women who smoked both before
and during pregnancy. We observed a dose-response relationship between the number of cigarettes
smoked per day during pregnancy and the odds of the aforementioned adverse birth outcomes;
neither were there significant differences in their occurrences among non-smokers and those who
smoked before but not during pregnancy. Moreover, smoking reduction during pregnancy relative
to its pre-gestation level did not influence the odds of the adverse birth outcomes. Our findings
emphasize a continued need for action against tobacco smoking during pregnancy.