Vaginal pH in pregnancy in women delivered at and before term

Influence of osmolarity and hydration on the tear resistance of the human amniotic membrane

The amnion is considered to be the load-bearing part of the fetal membranes. We investigated the influence of osmolarity of the testing medium and hydration on its fracture toughness. Mode I fracture tests revealed that physiological variations in the bath osmolarity do not influence the tear resistance of amnion, while larger changes, i.e. from physiological saline solution to distilled water, lead to a significant reduction of the fracture toughness. Uniaxial tensile tests on collagen hydrogels confirmed the reduction in toughness, suggesting that lower bath osmolarity triggers changes in the failure properties of single collagen fibers. Prenatal surgeries, in particular fetoscopic procedures with partial amniotic carbon dioxide insufflation, might result in dehydration of the amnion. Dehydration induced a brittle behavior; however, subsequent rehydration for 15 min resulted in a similar tear resistance as for the fresh tissue.

Association between increased antenatal vaginal pH and preterm birth rate: a systematic review

Background Worldwide, 14.9 million infants (11%) are born preterm each year. Up to 40% of preterm births (PTBs) are associated with genital tract infections. The vaginal pH can reflect changes in the vaginal milieu and, if elevated, indicates an abnormal flora or infection. Objective The aim of the study was to investigate whether an increased antenatal vaginal pH >4.5 in pre-labour pregnant women is associated with an increased PTB rate <37 completed weeks gestation. Search strategy Key databases included SCOPUS, EMBASE, MEDLINE, PsycInfo and the Cochrane Central Register of Controlled Trials, complemented by hand search, up to January 2017. Selection criteria Primary research reporting vaginal pH assessment in pre-labour pregnant women and PTB rate. Data collection and analysis Data extraction and appraisal were carried out in a pre-defined standardised manner, applying the Newcastle-Ottawa scale (NOS) and Cochrane risk of bias tool. Analysis included calculation of risk difference (RD) and narrative synthesis. It was decided to abstain from pooling of the studies due to missing information in important moderators. Main results Of 986 identified records, 30 were included in the systematic review. The risk of bias was considered mostly high (40%) or moderate (37%). Fifteen studies permitted a calculation of RD. Of these, 14 (93%) indicated a positive association between increased antenatal vaginal pH and PTB (RD range: 0.02-0.75). Conclusion An increased antenatal vaginal pH >4.5 may be associated with a higher risk for PTB. It is recommended to conduct a randomised controlled trial (RCT) to investigate the effectiveness of antenatal pH screening to prevent PTB. Tweetable abstract Pregnant women with an increased vaginal pH >4.5 may be at higher risk to experience preterm birth.

Requirements for germination of Clostridium sordellii spores in vitro

Clostridium sordellii is a spore-forming, obligately anaerobic, Gram-positive bacterium that can cause toxic shock syndrome after gynecological procedures. Although the incidence of C. sordellii infection is low, it is fatal in most cases. Since spore germination is believed to be the first step in the establishment of Bacilli and Clostridia infections, we analyzed the requirements for C. sordellii spore germination in vitro. Our data showed that C. sordellii spores require three structurally different amino acids and bicarbonate for maximum germination. Unlike the case for Bacilli species, d-alanine had no effect on C. sordellii spore germination. C. sordellii spores germinated only in a narrow pH range between 5.7 and 6.5. In contrast, C. sordellii spore germination was significantly less sensitive to temperature changes than that of the Bacilli. The analysis of the kinetics of C. sordellii spore germination showed strong allosteric behavior in the binding of l-phenylalanine and l-alanine but not in that of bicarbonate or l-arginine. By comparing germinant apparent binding affinities to their known in vivo concentrations, we postulated a mechanism for differential C. sordellii spore activation in the female reproductive tract.

The bacteriology of pre-labour rupture of membranes in a Nigerian teaching hospital

A prospective case control study that was conducted at the University of Ilorin Teaching Hospital, Ilorin, Nigeria, between 1st January and 31st December 2002. The purpose of this study was to determine the association and the pattern of bacteria/microorganisms in the aetiology of pre-labour premature rupture of membrane (PROM) in this centre. A total of 108 cases of PROM and 98 control cases that presented between 37 completed weeks' and 40 weeks' gestation were analysed. Pathogens were isolated in 48 patients, giving a recovery rate of 44.4%. The common pathogens include Gardnerella vaginalis (29.1%), Candida (23.0%) and Staphylococcus aureus (18.7%). Others were Streps. Pyogenes (16.6%), coagulase negative staphylococcus (CONS) (6.3%) and Klebsiella (6.3%). Only Candida and S. aureus were isolated in the controls. Ofloxacin and azithromycin were 100% active against all the isolated pathogens, while ampicillin was the least active. G. vaginalis was the most sensitive among the isolates while CONS and Klebsiella were the least sensitive. It is evident in this study that some pathogens were associated with PROM and that G. vaginalis was the most common organism and azithromycin was the only antibiotic with 100% sensitivity. We suggest that metronidazole should be added to azithromycin to cover for anaerobes in cases of PROM, where facilities for screening for anaerobes are not available.

The effect of pH on release of PGE2 from vaginal and endocervical preparations for induction of labour: an in-vitro study

OBJECTIVE

To study the effect of pH and precoating with obstetric cream on the release of prostaglandin E2 (PGE2) from commercially available triacetin and starch based gels, lactose based vaginal tablets and sustained release hydrogel polymer pessaries in-vitro.

DESIGN

A prospective observational study.

METHODS

PGE2 preparations held in dialysis bags were placed in Ringers lactate buffer and release of PGE2 into the buffer was measured over 8-12 h by radioimmunoassay. The hydrogel polymer pessary was also assessed after precoating with obstetric cream.

MAIN OUTCOME MEASURES

In-vitro PGE2 release at pH 7.4, pH 5.4 and pH 3.4. RESULTS The gel preparations provided rapid and reliable release, while the lactose based vaginal tablet provided much lower release of PGE2 with sudden and variable release occurring after 5-8 h, an effect which was enhanced at low pH. With the triacetin gel preparation, release of PGE2 was reduced at lower pH, while the starch based gel appeared to provide optimal release at pH 5.4. The hydrogel polymer pessaries provided linear release in-vitro and this was reduced at pH 3.4. In addition, precoating the sustained release hydrogel polymer pessaries with obstetric cream virtually abolished release of PGE2.

CONCLUSIONS

As the vagina is normally acid, these results suggest that vaginal pH could influence PGE2 release and this may result in variable clinical responses. In view of this, pH should be taken into account in the development of preparations for clinical use. Furthermore, the use of obstetric cream should be avoided when administering PGE2 preparations for induction of labour.

The relationship between prior cervical conization, cervical microbial colonization and preterm premature rupture of the membranes

The occurrence of prior cervical conization and the cervical microbial colonization was investigated in 38 women with idiopathic preterm labor, 35 women with preterm premature rupture of the membranes (PPROM) and 75 normal pregnant women at 26-34 weeks of gestation. Data were analyzed by Fisher's exact test (two-tailed). The frequency of prior cervical conization was significantly higher in PPROM patients compared to normal pregnant women (P < 0.001) and to patients in preterm labor (P < 0.01). Lactobacilli occurred with a lower frequency in patients with PPROM compared to patients in preterm labor (P < 0.05) and control patients (P = 0.0543)-and with a lower frequency in patients with prior cervical conization (P < 0.05). All other microorganisms occurred with the same frequencies in all groups. The absence of lactobacilli may indicate changes in the cervical flora, which could increase the risk of PPROM. Prior cervical conization may impair the antimicrobial defense-mechanisms in the cervix, which could facilitate ascending microbial colonization. This may lead to a release of prostaglandins and proteolytic enzymes and subsequently preterm labor and rupture of the membranes.

Vaginal and cervical pH in normal pregnancy and pregnancy complicated by preterm labor

A prospective study was performed in order to determine vaginal and cervical pH in pregnancy. In normal pregnancy vaginal pH (using a pH meter with connected glass electrode) was found to be between 3.8 and 4.0 (1 SD +/- 0.3) at the introitus, mid-vaginal, and at the anterior and posterior fornix. In patients with preterm labor (n = 50) or prolonged rupture of the membranes (PROM, n = 35) pH was increased significantly to 4.2-4.5 (1 SD +/- 0.7) resp. to 5.2-6.1 (1 SD +/- 0.8). Cervical pH ranges between 6.5 and 7.0 in all groups studied. Elevated pH values are due to disturbed vaginal flora. We recommend vaginal pH measurement for an quick detection of infection in cases with preterm labor and for clarifying PROM in suspicious cases.

Determination of vaginal pH by pH indicator strip and by pH micro electrode

Vaginal pH measurement is a screening method of vaginal infection in pregnancy. We tested two different methods of pH determination. In freshly taken vaginal fluid measurements were carried out with special pH indicator strips and pH micro glass electrode. About 100 microliters of vaginal fluid is enough when pH indicator strips are used, and 200 microliters when the micro electrode is used. The accuracy of the pH measurement by indicator strip is about 0.1-0.2 pH and by electrode 0.01 pH. Both methods show a good correlation between pH 4.0 to 7.0 (p = 0.0000). Until a pH of up to 4.3 we recommend the pH determination by indicator strips. In all cases with the possible risk of infection (pH values greater than 4.3) the micro electrode should be used.