Alcohol does affect fertility.

More Info: A study published in the British Medical Journal concluded that alcohol consumption among women attempting to become pregnant affected probability of conception.  In the study, 435 couples that were attempting to conceive for the first time were monitored for alcohol consumption.  Even women consuming fewer than five drinks per week experienced a lower probability of conception.

Does Smoking Affect Fertility?

Smoking can negatively affect fertility. Decreased blood flow to reproductive organs, early destruction of eggs and a reduction in estrogen can result in a decrease in fertility for women. Other studies and statistics also indicate that the woman's eggs may not be as viable when it comes to implantation as well.

The studies regarding the effects of smoking in male fertility are inconclusive. Although the research points to declining fertility as a result, it simply has not been studied as much. However, the medical community still warns there is the risk for men as well.      

Does Caffeine Affect Fertility?

Consuming over 300 milligrams per day of caffeine in any form has been shown to reduce your level of fertility by as much as 25 percent, according to the results of a recent research study on the habits of women who are trying to conceive. Other studies have come up with less conclusive answers, although most researchers agree that it is better to err on the side of caution while trying to conceive and avoid caffeine as much as possible.