As many couples know, becoming pregnant is not simply a matter of having intercourse near a selected date. Fewer than two-thirds of couples trying to conceive succeed within six months. Fortunately, 90% of women trying to get pregnant do so within 18 months.
There are dozens of factors that affect the odds of conception, some more important than others.
Caffeine intake does affect fertility for both men and women. Brewed coffee has between 100-300 mg of caffeine, while cappucino has between 300-400 mg and decaf (not surprisingly) has only 1-8 mg. Those concerned that caffeine might be an issue should limit themselves to no more than two cups per day.
Conditions in both men and women are about equally likely to be the reason pregnancy doesn't occur.
A small percentage of men have low sperm motility, a condition in which sperm cells don't actively move enough to make the trip up to the egg. Caffeine or excessive alcohol consumption can have some small effect on this, but in general the condition is either genetic or a temporary condition due to disease.
Or, a man may have a low sperm count, though again this is true of fewer than 10%. Heavy alcohol use can be a factor, but here again it's generally the result of inheritance or recent illness. In some cases this is due, for example, to high fever.
That's the true part of the statement that heat causes low sperm counts. This is temporary, though. The mythical part of the 'heat produces low sperm count' is the belief that hot tubs or underwear affects sperm count. The myth grew out of common laboratory observations that high temperature reduces sperm count in tests. But the temperature required is much higher than the shift produced by wearing jockey shorts or other lifestyle choices.
Fertility odds can be affected by issues women may experience, as well. 'Infertility' is often a matter of degrees. Very few women are completely infertile. For some women, the uterine environment causes implantation to be less likely. Endometriosis, a condition in which tissue from the uterine lining grows outside the uterus, is responsible for about 15% of low female fertility. Irregular ovulation is a problem for others. In about 20% of low fertility cases, some issue with the fallopian tubes is responsible.
For some, it's simply a matter of keeping better track of the menstrual cycle. Maintaining an accurate chart of basal body temperature and monthly events can help. They should be recorded at least once daily, preferably twice - once in the morning, once in the evening.
Being considerably overweight reduces a woman's chances of pregnancy, since it affects ovulation and overall hormonal factors. Body fat levels 10-15% over the normal range produces excess estrogen, which affects fertility. Hormonal imbalances in general, producing an irregular cycle or very heavy periods, can shift the odds. Anti-depressant and other medications can affect female fertility, as does heavy tobacco or alcohol consumption.
For those cases where the condition is not temporary, fertility treatments are an option. Most physicians won't intervene, however, unless the couple has been trying natural methods for at least 18 months. Fertility treatments themselves are not foolproof, nor are they entirely without risk.
If you've been trying to become pregnant for over a year without success, your first best course of action is to consult a physician.