Chlamydia is a vaginal infection caused by a parasite. Women with this infection may have no symptoms at all, but it can cause a variety of problems: tubal inflammation, pelvic inflammatory disease (PID), possible ectopic pregnancy, repeated miscarriage and infertility. If a woman has an infection at the time of giving birth, it can cause conjunctivitis in her baby. It is possible to screen for chlamydia (though this isn't done routinely). It can be successfully treated in pregnancy with the antibiotic erythromycin. It is always worth telling your doctor or midwife if you have any vaginal discharge you are worried about.