In the men, many studies have documented the effects of smoking on the number, motility and the shape of sperms. Many men who smoke can have normal sperm parameters on testing. Do not think that no harm has been done in these. The genetic material (DNA) in the sperm cells is packaged and stabilized by proteins (called protamines). In smokers, the ratio of the two types of protamines is altered and this leads to the sperm DNA being vulnerable to damage. Studies have also shown that the fertilizing capacity of sperms can be affected and the embryos can stop growing after a few days. The chances of pregnancy are therefore lower.
In women, the effects of smoking are stark. The quality as well as the quantity of eggs is affected. This leads to a delay in conception and increase in miscarriages. ICSI, a technique in which sperm is injected to achieve fertilisation, cannot overcome the damage caused and the chances of pregnancy after IVF/ICSI are almost half as that of non-smokers. Women who smoke also have an earlier menopause because of the effect of smoking on the ovaries.
Smoking is therefore discouraged in men and women who are yet to complete their family.