Background: Vulvovaginal candidiasis(VVC), or Vaginal thrush, is a vaginitis caused by the overgrowth of some opportunistic yeasts of the genus Candida spp. Australian Tea Tree Oil (TTO) is one of the most important essential oils that contain many compounds that are effective against many bacteria and fungi, which may match the effect of common antibiotics.        Objective: The aim of this study was to isolate and diagnose fungi that causing vaginal thrush, in pregnant women and to study the effect of (pregnancy and pregnancy sequence and age) on the rate of infection compared to non-pregnant, as well as to study the drug sensitivity of isolates towards a number of antifungal and compared that with the inhibitory effectiveness of tea tree oil.        Material and Methods: 75 vaginal swabs from pregnant women and 50 from non-pregnant women were collected at ages ranging from 17-65 years. The isolates were diagnosed using several methods, including the Vitek2 Compact system. 17 isolates were selected to study the inhibitory effect of ten antifungal agents, six of them were automatically tested by the Vitek 2 compact system, which contains a sensitivity test kit (AST-YS07 Card). The essential oil (TTO) was analyzed by GC-MS to detect its content of active compounds. The inhibitory effect of TTO was studied according to "Broth dilution" method to determine minimum inhibitory concentration (MIC) for it, the inhibitory effect of four concentrations of TTO (100%, 50%, 25%, 12.5 %) was also tested according to "well diffusion" method. This investigation also included a study of the mechanism of action (TTO).         RESULTS: The rate of infection among pregnant women was (41%) with the highest rate of infection during the third trimester of pregnancy, while the percentage of non-pregnant women was only 8%. Vaginal infection was also prevalent in the age group ranged between (17-29 years).The isolates showed resistance to (Ketoconazol, Terbinafine) while they were sensitive to (Nystatin, clotrimazol), as well as sensitive to all antifungal of (AST-YS07 Card). The analysis of the TTO using chromatogram showed that it contains 32 chemical compounds, most of them are monoterpene like (Terpinen-4-ol, 1, 8-Cineol). The MIC of TTO ranged between (4 - < 2 µl/ ml). The function of TTO is to destroy the structural structure of the cell membrane and change its permeability, thereby leakage of cellular components and cell death.        Conclusion: Pregnancy increases the rate of vaginal candidiasis in women, especially during the third trimester. TTO is highly effective in inhibiting the growth of opportunistic candida yeasts.