Testing for and treating sexually transmitted diseases (STDs) in pregnant women deserves special attention. Treatment possibilities are limited because of potential risks for the developing fetus, and because effects can differ in pregnant compared with non-pregnant women, re-infection may be missed because of the intrinsic delicacy of contact-tracing during pregnancy and because pregnant women are more reluctant to take the prescribed medication in its full dose, if at all. However, the devastating effects of some of these genital infections far outweigh any potential adverse effects of treatment. Although active syphilis has become a rarity in most Western countries, it is still prevalent in South America, Africa and South-East Asia. Benzathine benzylpenicillin (2.4 million units once or, safer, twice 7 days apart) is the treatment of choice, although patients with syphilis of longer standing require 3 weekly injections as well as extensive investigation into whether there has been any damage due to tertiary syphilis. Despite declining rates of gonorrhea, the relative rate of penicillinase-producing strains is increasing, especially in South-East Asia. The recommended treatment is intramuscular ceftriaxone (125 or 250 mg) or oral cefixime 400 mg. Despite good safety records after accidental use, fluoroquinolones are contraindicated during pregnancy. An alternative to a fluoroquinolone in pregnant women with combined gonorrhea and chlamydial infection is oral azithromycin 1 or 2 g. Azithromycin as a single 1 g dose is also preferable to a 7 day course of erythromycin 500 mg 4 times a day for patients with chlamydial infection. Eradication of Haemophilus ducreyi in patients with chancroid can also be achieved with these regimens or intramuscular ceftriaxone 250 mg. Trichomonas vaginalis, which is often seen as a co-infection, has been linked to an increased risk of preterm birth. Patients infected with this parasite should therefore received metronidazole 500 mg twice daily for 7 days as earlier fears of teratogenesis in humans have not been confirmed by recent data. Bacterial vaginosis is also associated with preterm delivery in certain risk groups, such as women with a history of preterm birth or of low maternal weight. Such an association is yet to be convincingly proven in other women. The current advice is to treat only women diagnosed with bacterial vaginosis who also present other risk factors for preterm delivery. The treatment of choice is oral metronidazole 1 g/day for 5 days. The possible reduction of preterm birth by vaginally applied metronidazole or clindamycin is still under investigation. In general, both test of cure and re-testing after several weeks are advisable in most pregnant patients with STDs, because partner notification and treatment are likely to be less efficient than outside pregnancy and the impact of inadequately treated or recurrent disease is greater because of the added risk to the fetus. Every diagnosis of an STD warrants a full screen for concomitant genital disease. Most ulcerative genital infections, as well as abnormal vaginal flora and bacterial vaginosis, increase the sexual transmission efficiency of HIV, necessitating even more stringent screening for and treating of STD during pregnancy.