How do smoking and drinking affect conception?

Tobacco Use Before Conception

Smoking, it has been found, increases the rate at which a woman's eggs become unusable and her risk of early menopause, both of which limit her number of fertile years. According to a study published by the British Medical Association, conception rates drop by as much as 40 percent in female smokers when compared to nonsmokers [source: Andalo]. And in addition to the nearly doubled rate of infertility, women take longer to conceive, and natural conception becomes more difficult. When conception does occur, the likelihood of giving birth to a low-birth weight baby is higher for smokers. Smoking before and during pregnancy also increases miscarriage rates, as smoking increases the chance for an egg to have chromosomal abnormalities.

It takes two to make a baby, though, and a man's health and lifestyle can affect fertility and conception. Smoking is linked to low sperm count, low sperm motility (slow movement) and sperm with damaged DNA -- all three problems reduce the quality of sperm and are known to cause fertility issues. Researchers at the University of Saarland found that men who smoked a minimum of 20 cigarettes every day had lower concentrations of protamines, two proteins found in sperm, than men who didn't smoke at all. These protamines are thought to be an integral part of cell division, and they ensure the correct chromosomal formation during conception. In addition to the number of ways smoking is bad for your health, it's bad during conception because it changes the way DNA is handled.

For the best chance of conceiving and carrying a baby to term, it's a good idea to start a smoking cessation plan. Some health professionals recommend you stop about two to three months before trying to conceive to get the full benefits of quitting.

Keep reading to learn how drinking alcohol affects your chances of becoming pregnant.