Smoking fathers are less likely to have a son

If your husband is a heavy smoker, you may be much less likely to have a son.  Men who were smokers were much less likely to produce male embryos, in a study of couples using IVF with PGD (preimplantation genetic diagnosis):

• The men's semen samples were analyzed to determine the X:Y ratio, the number of boy-producing compared to girl-producing sperm.  All samples, smokers and non-smokers alike, were found to have an equal amount of X and Y sperm. 
  
• The sperm samples were then prepared for fertilization using the swim-up technique, which separates the healthiest, most motile sperm cells from abnormal or slow-moving sperm cells. 
  
  Among smokers, the healthy portion of sperm was found to have a higher proportion of X sperm. 
  

The resulting embryos were analyzed using PGD, and here are the results:

• 53% male embryos were produced by non-smoking fathers.
• 32% male embryos were produced by smoking fathers.

• Smoking habits of parents and male: female ratio in spermatozoa and preimplantation embryos
  Human Reproduction