Probiotics are dietary health supplements containing potentially beneficial live microorganisms, which when administered in adequate amount confer health benefits to the host. The most common type of microbe used is lactic acid producing bacteria. As a result, these bacteria are able to convert sugars (lactose) into lactic acid. Prebiotics, on the other hand are non-digestible food ingredients that benefit the host by selectively stimulating the growth or activity of one or a limited number of bacteria in the colon. Probiotics and prebiotics share a unique role in human nutrition, largely focusing on manipulation of populations or activities of the bacteria that colonize our bodies. Probiotics can be considered as a natural means for repairing the deficiencies in the gut and vaginal flora. This is primarily discussed in this chapter. This chapter also discusses the potential benefits of probiotics; their adverse effects as well as their role in pregnant women.