During pregnancy periodontal tissues may become more susceptible to internal and external factors promoting inflammation. Changes in hormone levels, alterations in the periodontal tissue structure and a predisposition to dilating blood vessels during pregnancy may lead to a painful inflammation as a response to a slightest amount of biofilm. Tumor gravidarum emerges in 5% of pregnant women during the first or second trimester - it may recede and fade completely right after the labour when hormone levels normalize. This paper explains the aetiology and potential risk factors of pregnancy gingivitis.