Tobacco Harm Reduction: Not During Pregnancy (Revisited)

In May, I discussed a 2003 Swedish study reporting that pregnant women who use snus are at risk for slightly smaller babies, and have modestly elevated risks for premature delivery and preeclampsia (read the post here). Two new studies from Sweden also document that snus use has risks for the developing baby and should be avoided.

Both studies are based on over 600,000 pregnancies documented in the Swedish Medical Birth Register from 1999 to 2006, and both are authored by Anna-Karin Wikström and colleagues from the Karolinska Institute.

The first study, published in the British Journal of Obstetrics and Gynaecology (sic) (abstract here), examined the effect of tobacco use on the risk for very premature (less than 32 weeks) or moderately premature (32-26 weeks) births. It showed that snus users had a modestly elevated risk for a very premature birth (adjusted odds ratio, aOR = 1.38, 95% confidence interval = 1.04 – 1.83). The risk among light smokers (1-9 cigarettes per day) was 1.60 (CI = 1.42 – 1.81), and the risk among heavy smokers (10+ cigarettes) was 1.90 (CI = 1.61 – 2.25). The study also showed that snus users had an elevated risk for a moderately premature birth of 1.25 (CI = 1.12 – 1.40), which was intermediate between light smokers (aOR = 1.18, CI = 1.12 – 1.24) and heavy smokers (aOR = 1.45, CI = 1.35 – 1.56).

The second study, published in Epidemiology (abstract here ), examined the effect of tobacco use on the risk for stillbirth, which is the death of a baby during pregnancy. It showed that women who were snus users had a modestly elevated risk (aOR = 1.57, CI = 1.03 – 2.41), which was again intermediate between light smokers (aOR = 1.15, CI = 0.91 – 1.45) and heavy smokers (aOR = 1.85, CI = 1.39 – 2.46).

The study I discussed in May found that snus use was associated with preeclamsia, but Wikström and colleagues did not report a statistically significant elevated risk. In addition, they reported that snus users did not have elevated risks for bleeding or for infants who were small for their gestational age, both of which are seen in light and heavy smokers.

In general snus use is vastly safer than smoking, but pregnant women should refrain from using all tobacco products.