Fertility after miscarriage
A miscarriage itself doesn't effect a woman's fertility. It can, however, be an indicator of fertility issues if there are multiple losses. In fact, women are generally thought to be extra fertile in the 4-6 weeks following a miscarriage because of hormone levels. Most doctors advise waiting at least a cycle or two before trying again, though. The uterine lining needs time to recover from the loss, so while you may get pregnant right away that baby may not be able to implant properly.
Statistically 1 in 3 pregnancies will end in miscarriage, so it's a lot more common then women think. Over half of all miscarriages are caused by a chromosomal abnormality. Basically, a genetic fluke that's out of your control. Usually the next pregnancy will be healthy.
If you do have more then one miscarriage in a row (or 3+ in your lifetime) this could indicate an underlying issue. Physical abnormalities of the uterus or cervix can make it hard to sustain pregnancy. Hormone imbalances, Immunologic Disorders, Thyroid problems, infections, and high-risk lifestyles (drugs, smoking, drinking, etc.) can also lead to chronic miscarriage.
We got pregnant 2 months after our first miscarriage and then lost that baby at 6 weeks. We wanted to wait until we had answers before trying again and my doctor thought I could have an issue producing enough progesterone to sustain a pregnancy into the second trimester. We tried again about 2 months later, got pregnant right away, took progesterone suppositories, and had a healthy baby that next June :)
There is also the fact that many women miscarry before the first 12 weeks and may not have even known they were pregnant yet. If I hadn't been trying I may have though that my period was just a week or two late.