Women are often seen visiting a gynecologist due to vaginal discomfort. Vagina is a likely site for infections by potentially pathogenic bacteria since it is close to the anus. Therefore, there is a dire need for a vaginal protection system that can help prevent the proliferation of pathogens.1

The characteristic pH of women of reproductive age is 3.5 to 4.5.1 Women with a vaginal pH > 5.0 or > 4.5 and a Nugent score of 9–10 have been found to have significantly increased rates of preterm birth and birth weight <2500 g or <1500 g.2 Maintaining the ideal vaginal pH is therefore essential to prevent these complications. Maintenance of a 3.5 to 4.5 acidic pH also serves as a vaginal protection system that hinders the growth of potentially pathogenic organisms, while providing a suitable environment to acidophilus bacilli.1 Under these conditions, Acidophilus bacilli highly metabolize and produce large amounts of lactic acid by glucose anaerobic fermentation. Lactic acid keeps its acidic pH and prevents uncontrolled growth of other bacteria present in the vagina.1

Bacterial vaginosis (BV) is a common infection and has been associated with obstetric and gynecologic complications, including preterm labor and delivery, preterm premature rupture of membranes, spontaneous abortion, chorioamnionitis, postpartum endometritis, post-cesarean delivery wound infections, postsurgical infections, and subclinical pelvic inflammatory disease.3 BV is marked by altered vaginal flora. It is characterized diminished or absent flora of lactobacilli, resulting in increased vaginal pH, and increased colonization of several anaerobic or facultative microorganisms, especially Gardenerella vaginalis, Prevotella sp, Bacteroides sp, Mobiluncus sp, gram positive cocci, and genital mycoplasma (Mycoplasma hominis and Ureaplasma urealyticum).2

Thus, it is important to achieve the characteristic pH of women of reproductive age, i.e., 3.5 - 4.5, and this can be achieved by the presence of a sufficient amount of lactic acid in the vagina. Lactic acid has an important role in maintaining a medium that favors the growth of lactobacilli in the vagina.1 Lactic acid prevents the growth of fungi, protozoa, Haemophilus and other pathogenic bacteria, which usually need a pH of >6.0. Lactic acid is the key element in maintaining vaginal health.1

References

1. Haya J, García A, López-Manzanara C, et al. Importance of Lactic Acid in Maintaining Vaginal Health: A Review of Vaginitis and Vaginosis Etiopathogenic Bases and a Proposal for a New Treatment. Open Journal of Obstetrics and Gynecology 2014;4:787-799.
2. Krauss-Silva L, Almada-Horta A, Alves MB, et al. Basic vaginal pH, bacterial vaginosis and aerobic vaginitis: prevalence in early pregnancy and risk of spontaneous preterm delivery, a prospective study in a low socioeconomic and multiethnic South American population. BMC Pregnancy and Childbirth 2014;14:107.
3. Yudin MH, Money DM, Boucher M, et al. Screening and Management of Bacterial Vaginosis in Pregnancy. Available from: https://sogc.org/wp-content/uploads/2013/01/gui211CPG0808.pdf.