Smoking, Alcohol, Caffeine, and Street Drugs
Many medical conditions have alternative treatment options for those wishing to conceive. If you have diabetes or thyroid disease, it is imperative for these conditions to be optimally treated before trying to conceive. (Learn more about managing common conditions that may affect pregnancy.)
Radical changes in sexual behavior over the last few decades have resulted in a dramatic rise in the prevalence of sexually transmitted infections, sometimes referred to as genitourinary tract infections. Many of these STIs produce symptoms that allow prompt diagnosis and treatment, while others cause silent infection that may adversely affect fertility and the health of the fetus and newborn. Ask your doctor which infections you should be screened for.
None of it is good for you, and all of it—smoking, alcohol, caffeine, and street drugs—is especially dangerous for a developing fetus.
Smoking: According to The American Society of Reproductive Medicine:
Virtually all scientific studies support the conclusion that smoking has an adverse impact on fertility. The prevalence of infertility is higher, and the time it takes to conceive is longer, in smokers compared to nonsmokers. In addition, the impact of secondhand smoke exposure is comparable to the effects of smoking. Smoking appears to accelerate the loss of eggs and may advance the time of menopause by several years. Pregnant smokers are more likely to have low birth weight babies, premature birth, and babies with congenital defects. The incidence of sudden infant death syndrome (SIDS) also increases in households where someone smokes.
Men who smoke cigarettes have a lower sperm count and motility and increased abnormalities in sperm shape and function.
Alcohol: Some studies have shown that even drinking as little as two drinks of alcohol a week can adversely affect fertility. Heavy drinking can lead to the loss of periods altogether, and drinking more than 14 units per week before the developing embryo is embedded in the uterus increases the chance of miscarriage. Not to mention that around 40 percent of male sub fertility is actually caused by excessive alcohol intake, which lowers sperm count and motility. So if you are trying to get pregnant you are strongly advised to cut out alcohol altogether.