If contracted, babies can develop infections in their eyes, ears, lungs and genitals. Eye infections lead to conjunctivitis and lung infections leave pneumonia a distinct possibility. One thing to mention, if someone does not have symptoms, doesn't mean you can't get it. As stated before, often it is asymptomatic. The primary way of contracting Chlamydia is unprotected Vaginal, Anal and Oral sex.
Women are at greater risk contracting it because they are infected internally.
The most obvious way is to use protection such as Condoms. Limiting the number of sexual partners greatly will reduce the risk of contracting Chlamydia. If you do have Chlamydia, it is best to tell your partner so that others don't get it, or you yourself don't get it again after you've been treated. A Pap smear is NOT for detecting Chlamydia. Treatment includes antibiotics.