That case of chlamydia you had in your twenties or the urinary tract infection that sent your partner to the doctor last year can inflict lasting reproductive woes (including infertility, pregnancy complications and birth defects).

The best approach is to avoid infections altogether. Practicing safe sex with condoms, for example, can fend off most fertility-robbing sexually transmitted diseases (STDs).

Because infection dodging isn't always possible, you should get a test for STDs each year when you get your annual gynecological exam and Pap test. You may also want to get tested for some specific infections before you conceive. Chances are your doctor will test for many of the following sexually transmitted infections plus rubella via a simple blood test during your first prenatal visit. But don't count on a test for everything (different states have different requirements).

Because many infections fester for years without symptoms, the earlier you get checked -- even months or years before you're ready to get pregnant -- the greater your changes of catching something before reproductive harm is permanent. "Many infections can be tested for and treated ahead of time through antibiotics or immunizations so they don't cause problems," says Nancy Green, MD, medical director of the March of Dimes.

Sexually Transmitted Infections
Chlamydia. Transmitted through unprotected sex with an infected partner, chlamydia infections often smolder undetected for years. In fact, as many as three of every four infected women and 40 percent of infected men don't know they have chlamydia. Unfortunately, discovery often comes after the damage is already done. "Chlamydia is a huge problem," notes Mitchell N. Essig, MD, an obstetrics and gynecology instructor at Albert Einstein College of Medicine at Yeshiva University in the Bronx, who also has a private Manhattan practice in reproductive endocrinology and infertility. "It's the most common and most insidious of STDs."