Parental cigarette smoking before and during pregnancy in a cohort of 21 472 pregnancies.

Smoking during pregnancy is one of the leading causes for adverse pregnancy outcomes. We studied parental smoking both before and during pregnancy in a retrospective cohort of 21 472 singleton pregnancies. Although most smoking women (74%) ceased tobacco use, there was possible gestational exposure to maternal cigarette smoking in every fifth pregnancy. Continued smoking throughout pregnancy was more prevalent in the partners (22%) than in the pregnant women (7%). The smoking behaviour of the women, especially the number of cigarettes smoked per day (CPD), before and in early pregnancy predicted the continuation of smoking throughout the pregnancy and could be used in identifying high risk groups. In addition, their partner's smoking habits both before and during pregnancy, were associated with the likelihood that the woman would continue to smoke during her pregnancy (rs ≈ 0.4). Furthermore, continued smoking of both parents were associated with decreased birth weight, head circumference and Apgar score, and increased duration of hospital stay and need for special care after birth. Consequently, addressing the lifestyles of both parents in the health care and maternity clinics could help in reducing maternal cigarette smoking during pregnancy and the adverse pregnancy outcomes associated with smoking.