The scariest part of deciding to try to get pregnant after a miscarriage is facing the chances of a second miscarriage. One miscarriage is an awful enough experience -- it's only natural if you hesitate when facing the risk that it could happen again.
The good news, however, is that having one miscarriage usually doesn't mean higher chances of another one. Still, the answer depends partly on what kind of pregnancy loss you had.
First Trimester Miscarriage
Doctors believe that most first-trimester miscarriages (including chemical pregnancies) are due to non-recurring chromosome problems in the developing baby. If your last pregnancy ended in first-trimester miscarriage, your odds of having a normal pregnancy next time around are probably the same as they were before you miscarried. Although there will always be some risk of miscarriage, you will not automatically be considered at higher risk than anyone else in your age group.
Second Trimester Miscarriage or Stillbirth
Studies show that women who have had a second trimester miscarriage or later pregnancy loss may have a higher than average risk of having a repeat miscarriage or preterm delivery in the next pregnancy. This doesn't mean that you should fear getting pregnant again; the odds are higher that your next pregnancy will be just fine. But you should be sure to work closely with your doctor and seek prenatal care on your doctor's recommended schedule, which may include extra monitoring to watch for complications.
If your first pregnancy loss was due to ectopic pregnancy, there is about a 10% to 20% chance of having another one (as compared to a roughly 1% chance for someone who has never had an ectopic pregnancy). You should see a doctor early on when you are pregnant again to confirm that the new pregnancy is implanted in your uterus. But once you get that confirmation, your miscarriage risk won't be any higher than average.
If You Do Have a Second Miscarriage
Sadly, things aren't always fine the next time around and a small percentage of women will go on to have one or more subsequent miscarriages. If this does happen to you, the chances are still high that you will eventually have a successful pregnancy, but talk to your doctor to find out if you need testing for causes of recurrent miscarriages before you get pregnant again.
Edlow, Andrea G. , Sindhu K. Srinivas, Michal A. Elovitz. "Second-trimester loss and subsequent pregnancy outcomes: What is the real risk?" AJOG Volume 197, Issue 6, Pages 581.e1-581.e6 (December 2007).
Medical FAQ. Ectopic Pregnancy Trust. Accessed Oct 8, 2009. http://www.ectopic.org.uk/medical_information/faq.htm
Problems in pregnancy - Miscarriage. Tommy's. Accessed Oct 8, 2009. http://www.tommys.org/Page.aspx?pid=262