Background Maternal smoking is still a major public health problem posing the risk of several negative health outcomes for both the pregnant woman and her offspring. The prevalence of maternal smoking in Denmark and other high-income countries has decreased continuously since the 1980s, and a prevalence below 10% of women who continue to smoke during pregnancy has been reported in studies after 2010. Previous studies have shown that low socioeconomic status is associated with maternal smoking. Information from the Danish Birth Register about maternal smoking shows that the prevalence of women who report to smoke in pregnancy has decreased continuously with 23.3% who reported ever smoking in pregnancy in 2000, 12.9% in 2010 and 9.0% in 2017. The aim of this study was to estimate the prevalence of maternal smoking at the time of conception and at 20 weeks of gestation in a regional Danish population, to describe differences in maternal characteristics among smokers, quitters and never-smokers, and to estimate predictors of smoking at the time of conception. Methods A cross-sectional study was conducted among pregnant women receiving antenatal care at the Department of Obstetrics, Zealand University Hospital, Denmark from August 2015 to March 2016 ( n = 566). The main outcome was smoking at the time of conception and at 20 weeks of gestation. The questionnaire also collected information about maternal, health-related and sociodemographic characteristics. Descriptive analysis was conducted, and multivariate logistic regression analysis was used to assess the potential associated predictors (adjusted odds ratio). Results The prevalence of self-reported smoking at the time of conception was 16% ( n = 90) and 6% smoked at 20 weeks of gestation ( n = 35), as 61% of smokers quit smoking during early pregnancy. Multiple logistic regression analysis showed that significant predictors for smoking at conception were the socioeconomic factors; ≤12 years of education, shift work and being unemployed. Conclusion The prevalence of self-reported maternal smoking in this regional Danish population of pregnant women is lower than seen in previous studies. However, predictors for smoking at the time of conception remain to be factors of low socioeconomic status confirming a social inequality in maternal smoking. Women at risk of smoking during pregnancy must be identified in early pregnancy or even before pregnancy and be offered interventions to help them quit smoking.

Objective To assess indicators of fetal growth and risk of preterm birth in children of parents with rheumatoid arthritis (RA). Methods Through linkage of Danish national registries we identified all children born in Denmark between 1977 and 2008. We used general linear regression models to estimate mean differences in indicators of fetal growth among children having a parent with RA compared to unexposed children. Odds ratios of preterm birth were calculated by a logistic regression model. Results Of the 1,917,723 children included, a total of 13,556 children were exposed to maternal RA or maternal preclinical RA. Children exposed to maternal RA (2,101) had approximately similar length, head and abdominal circumference at birth, compared with children of mothers without RA. Birth weight was 87 gram lower (−87.04 g; 95% CI, −111.23; −62.84) and placenta weight was 14 gram lower (−13.45 g; 95% CI, −21.46; −5.43). Rather similar results were found in children exposed to maternal preclinical RA (11,455). Compared with unexposed children a higher risk of preterm birth was found in children exposed to maternal RA and maternal preclinical RA respectively (OR, 1.48; 95% CI,1.20;1.84 and OR, 1.32; 95% CI,1.07;1.64). No associations were found with paternal RA. Conclusion Children exposed to either maternal RA or maternal preclinical RA are more often born preterm. However, indicators of fetal growth measured at birth were only slightly lower than in unexposed children.

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