For couples that are not able to conceive, even though they have not used any form of birth control, it is a prime possibility that the couple is suffering from infertility. For women that are under 35 years of age, the amount of time before seeking fertility treatment can be a little more laxed. Women who are over 35 years of age or older, not being able to conceive after six months are considered to be suffering from "sub-fertility".
Most medical practitioners believe that 50% of fertility problems are caused by the woman and her reproductive system. This could be due to scar tissue in the fallopian tubes, ovaries, etc. While 35% is considered to be due to a low sperm count. The remaining 15% is just not known despite all physical testing. When this happens, it can be frustrating for both the medical practitioner and the couple. Most medical practitioners usually consider the last 15% to be some mixture of the male and female infertility factors.
Timing is of the esscense, especially if the woman is over 35 years of age. If the woman experiences a miscarriage, the couple should seek genetic counseling, especially if miscarriage runs in the woman's family. It is important for a couple to be completely honest to their medical doctor about their lifestle, whether or not they use drugs, alcohol, or have multiple sexual partners.