Little is known regarding the possible harmful effects of Borrelia infections in pregnancy, since such a risk analysis is difficult to perform. Transplacental transmission of Borrelia burgdorferi has been documented in several animal studies. Therefore, it had been thought that fetal infection and teratogenicity was possible from B. burgdorferi, especially considering the similarities between Lyme borreliosis and syphilis. However, several clinical, serological, and epidemiological studies have failed to confirm a causal association between B. burgdorferi infection and a pregnancy adverse outcome. Moreover, there have been no reported cases of transmission of Borrelia via breast milk. However, the therapeutic approach to pregnant women with Lyme disease should be antibiotic treatment, according to the clinical manifestation and the timing of the tick bite. An effective vaccine is not yet available and the prevention of Lyme borreliosis depends on public and physician education, and appropriate antibiotic therapy during pregnancy.