Smoking in pregnancy--effects on birth weight and on cyanide and thiocyanate levels in mother and baby.

A total of 45 expectant mothers (20 smokers and 25 non-smokers) and their babies was studied and, after 14 smokers and 14 non-smokers had been closely matched for age, height, parity and social class, significant differences were observed between smokers and non-smokers in the birth weights of the babies and in cyanide and thiocyanate levels in maternal blood and urine.