Wednesday, July 10, 2013

Snus Effect on Newborn Birth Weight: Very Small

Three years ago I discussed several Swedish studies reporting that pregnant women who use snus are at risk for (1) slightly smaller babies and premature delivery and preeclampsia (here); and (2) 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 and was based on over 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 of never users.  This is approximately the same magnitude found in the earlier study I discussed (here).  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 PLoS (Public Library of Science) One (here).  The publisher banned studies funded by the tobacco industry, a policy I labeled as unscientific three years ago (here).


Jonathan Bagley said...

I've never understood this whole birth weight argument. I was the first born and weighed less than 7lbs. My sister was the third born and weighed 8lbs. 20 gms is less than 1 oz. Am I worse off? I'm now 56 years old, fine boned, 6' 1.5" with a bmi of 22. When I was born, my weight wasn't considered abnormal, yet now, babies are monsters. Can somebody please explain all this?

Dale Hanson said...

@Jonathan I believe when people discuss birth weight and being small, they are also thinking that the baby is premature, which could mean health complications.

Andy Gray said...

I think that their conclusion that "snus is a healthier alternative to smoking during pregnancy" is a dumb statement to make. Just because it's healthier than smoking does not make it healthy, which is how a lot of people will take that statement.