Analysis Effect of snus use on newborn birth weights? Real, but very small
Three years ago, I discussed several Swedish studies reporting that pregnant women who use snus are at risk for:
- Slightly smaller babies, premature delivery and preeclampsia (here); and
- Premature birth and stillbirth (here).
Although the risks were lower than those from smoking, I advised that “pregnant women should refrain from using all tobacco products.”
A new Swedish study confirms that the effect of snus use on birth weight is small, but the researchers made a gross oversight in their journal article.
The new study was conducted at Lund University, based on more than 900,000 births chronicled in the Swedish Birth Registry from 2002 to 2010. It looked at the effect of snus use on birth weight with a conventional analysis and with a special analysis in which mothers had used or not used snus during two different pregnancies (a “sibling analysis”).
Conventional analysis found that snus users’ babies weighed a statistically significant 47 grams (about 1.7 ounces) less than those who had never used it. This is approximately the same magnitude found in the earlier study I discussed. However, there was only a 20 gram reduction in the sibling analysis, which was not significant.
The Lund authors emphasize:
Our findings should not be interpreted as suggesting that the use of snus is a healthier alternative to smoking during pregnancy.
This might be an appropriate statement, but for the fact that the researchers report no attempt to compare and analyze the data they held on the births experienced by more than 100,000 smokers.
Exaggerating small risks but failing to directly compare smokeless tobacco users with smokers seems to be endemic among many scientists with anti-tobacco leanings. Datasets from the Karolinska Institute and the American Cancer Society contain risk information for both smokeless users and smokers, but staff at these organizations refuse to report comparable risks for these two groups.
The Lund University study appears in the Public Library of Science’s PLoS One. The publisher banned studies funded by the tobacco industry, a policy I labeled as unscientific three years ago.
