Scientists in Denmark and Japan have found that whether young parents smoke is related to the ratio of babys' gender  If both parents do not smoke, the ratio of boys to girls is 1 214 to 1  If both parents smoke more than 20 cigarettes a day, the ratio of  boys to girls drops to 0 823 to 1  Even if only one person smokes and is not addicted to cigarettes, the probability of having a boy will decrease  The reason may be that the sperm or male embryos carrying the Y chromosome are more likely to be harmed by smoking
Except for smoking , emotional stress and environmental pollution factors can also cause a decline in the proportion of male babies
Smoking parents have a lower chance than no-smoking parents to have a boy.