Smoking in pregnancy and vitamin B 12 metabolism.

In pregnancy the level of serum vitamin B(12) is lower in women who smoke than in non-smokers. This finding occurs independently of social class, parity, or level of haemoglobin. In addition, the mean serum B(12) level tends to be less in women who are anaemic and is less in those women who have smaller babies. These findings may be an effect of the cyanide content of tobacco smoke, since cyanide may be detoxified by a mechanism which depletes the stores of vitamin B(12) in the body.