How do smoking and drinking affect 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.

Similar to how smoking affects your ability to become pregnant, drinking alcohol before trying to become pregnant may also have adverse affects on conception. While the effects of alcohol consumption during pregnancy are well known -- the physical, behavioral and cognitive problems known as Fetal Alcohol Spectrum Disorders -- drinking before getting pregnant can also cause problems. Alcohol consumption can lower your chances of conception, and it's also linked with higher chances of miscarriage.

A study published in the British Medical Journal found that women who drank more than 10 alcoholic beverages per week had impaired fertility, and even those women who drank five or fewer drinks per week had a harder time getting pregnant than women who didn't drink at all while trying to conceive [source: Jensen et al].

Alcohol appears to affect estrogen and other reproductive hormones in the body, making monthly cycles longer and anovulatory cycles -- menstrual cycles during which ovulation doesn't occur -- more common. If ovulation doesn't occur, a woman's ovary doesn't release an egg. When this happens, a woman literally can't become pregnant, no matter how hard she tries.

Men who drink alcohol may also suffer from alcohol-related fertility issues such as low sperm count and low sperm motility. What does this mean when you're thinking about getting pregnant? A man's ejaculate contains fewer sperm, and a higher percentage of the available sperm are unable to make the long journey to fertilize a woman's egg.

So what's a couple to do? The best thing is to stop drinking alcohol when you decide to try to get pregnant, and just as with smoking cessation, some health professionals will recommend stopping about two to three months before trying to conceive to get the full benefits.

For more information about how drinking and smoking affect conception, check out the great links on the next page.