Pregnant women frequently develop increased vaginal discharge. his may be a physiological discharge, described in Chapter 4 (p. 51), but should be diferentiated from symptomatic vaginitis, which is also common in pregnancy. Fortunately, vaginitis is prevented in part by normal vaginal lora. To better understand this, studies of the composition and function of the normal vaginal microflora are currently underway with the Vaginal Human Microbiome Project (Huang, 2014).
Not an infection in the ordinary sense, bacterial vaginosis (BY) is a maldistribution of normal vaginal flora. With BV, num bers of lactobacilli are decreased, and anaerobic bacteria spe cies are overrepresented. hese anaerobes include Gardnerela,
Prevotela, Mobiluncus, and Bacteroides species; Atopobium vagi nae; and BV-associated bacteria, provisionally named BVAB 1,
BVAB2, and BVAB3. hese last three are newly recognized bacteria found in women with BV (Fredricks, 2005).
Molecular ribosomal RNA gene sequencing techniques have greatly aided this understanding of the vaginal lora, also called the vaginal m icro biota. Five types of vaginal microbiota exist, referred to as communiy state ypes (eSTs). And, a woman can be categorized to one of these ive CSTs based on her vaginal microbiota composition (Ravel, 2011). Researchers have begun to quantiy the risk of BV by these CST groups. Speciically, CST s I, II, III, and V are rich in lactobacilli. In contrast, CST IV is a heterogeneous microbiota of strict anaerobes and is associated with BV. CSTs vary racially, and CST IV is also the most common in asymptomatic, healthy black women (Fettweis, 2014). Pregnancy-related changes in vaginal micro biota are also being defined and may hold keys to adverse BV-related pregnancy outcomes, discussed subsequently (Romero, 2014).
Of childbearing-aged women in the United States, nearly 30 percent have BV. In black women, the prevalence approximates 50 percent (llsworth, 2007). Most women are asymptomatic, but a foul, thin vaginal discharge is a typical complaint. Associated risk factors are douching, multiple partners, smoking, and altered host immunity (Desseauve, 2012; Koumans, 2007; Murphy, 2016) .
For clinical diagnosis of BV, three of the four following criteria are present: (1) vaginal pH >4.5; (2) a thin, milky, noninlammatory vaginal discharge; (3) > 20 percent clue cells seen microscopically; and (4) a fishy odor ater addition of 10-percent potassium hydroxide to vaginal secretion samples (Amsel, 1983). The last is described as a positive "whif test." Likewise, alkalinity of seminal fluid and blood are responsible for foul-odor complaints ater intercourse and with menses in afected women. Clue cells are vaginal epithelial cells containing many attached bacteria, which create a poorly deined stippled cellular border (Fig. 65-6). he higher vaginal pH stems from diminished acid production by lactobacilli. Similarly, Trichomonas vaginalis infection is also associated with anaerobic overgrowth and resultant elaborated amines. hus, women diagnosed with BV should have no microscopic evidence of trichomoniasis (see Fig. 65-6).