A controlled study of genital mycoplasmas in amniotic fluid from patients with intra-amniotic infection

Clinical chorioamnionitis at term: definition, pathogenesis, microbiology, diagnosis, and treatment

Clinical chorioamnionitis, the most common infection-related diagnosis in labor and delivery units, is an antecedent of puerperal infection and neonatal sepsis. The condition is suspected when intrapartum fever is associated with two other maternal and fetal signs of local or systemic inflammation (eg, maternal tachycardia, uterine tenderness, maternal leukocytosis, malodorous vaginal discharge or amniotic fluid, and fetal tachycardia). Clinical chorioamnionitis is a syndrome caused by intraamniotic infection, sterile intraamniotic inflammation (inflammation without bacteria), or systemic maternal inflammation induced by epidural analgesia. In cases of uncertainty, a definitive diagnosis can be made by analyzing amniotic fluid with methods to detect bacteria (Gram stain, culture, or microbial nucleic acid) and inflammation (white blood cell count, glucose concentration, interleukin-6, interleukin-8, matrix metalloproteinase-8). The most common microorganisms are Ureaplasma species, and polymicrobial infections occur in 70% of cases. The fetal attack rate is low, and the rate of positive neonatal blood cultures ranges between 0.2% and 4%. Intrapartum antibiotic administration is the standard treatment to reduce neonatal sepsis. Treatment with ampicillin and gentamicin have been recommended by professional societies, although other antibiotic regimens, eg, cephalosporins, have been used. Given the importance of Ureaplasma species as a cause of intraamniotic infection, consideration needs to be given to the administration of antimicrobial agents effective against these microorganisms such as azithromycin or clarithromycin. We have used the combination of ceftriaxone, clarithromycin, and metronidazole, which has been shown to eradicate intraamniotic infection with microbiologic studies. Routine testing of neonates born to affected mothers for genital mycoplasmas could improve the detection of neonatal sepsis. Clinical chorioamnionitis is associated with decreased uterine activity, failure to progress in labor, and postpartum hemorrhage; however, clinical chorioamnionitis by itself is not an indication for cesarean delivery. Oxytocin is often administered for labor augmentation, and it is prudent to have uterotonic agents at hand to manage postpartum hemorrhage. Infants born to mothers with clinical chorioamnionitis near term are at risk for early-onset neonatal sepsis and for long-term disability such as cerebral palsy. A frontier is the noninvasive assessment of amniotic fluid to diagnose intraamniotic inflammation with a transcervical amniotic fluid collector and a rapid bedside test for IL-8 for patients with ruptured membranes. This approach promises to improve diagnostic accuracy and to provide a basis for antimicrobial administration.

Prevention and Therapy of Preterm Birth. Guideline of the DGGG, OEGGG and SGGG (S2k Level, AWMF Registry Number 015/025, September 2022) - Part 2 with Recommendations on the Tertiary Prevention of Preterm Birth and on the Management of Preterm Premature Rupture of Membranes

Aim The revision of this guideline was coordinated by the German Society for Gynecology and Obstetrics (DGGG), the Austrian Society for Gynecology and Obstetrics (OEGGG) and the Swiss Society for Gynecology and Obstetrics (SGGG). The aim of the guideline is to improve the prediction, prevention and management of preterm birth based on evidence from the current literature, the experience of members of the guidelines commission, and the viewpoint of self-help organizations. Methods The members of the contributing professional societies and organizations developed recommendations and statements based on international literature. The recommendations and statements were presented and adopted using a formal process (structured consensus conferences with neutral moderation, written Delphi vote). Recommendations Part 2 of this short version of the guideline presents statements and recommendations on the tertiary prevention of preterm birth and the management of preterm premature rupture of membranes.

Management of clinical chorioamnionitis: an evidence-based approach

This review aimed to examine the existing evidence about interventions proposed for the treatment of clinical chorioamnionitis, with the goal of developing an evidence-based contemporary approach for the management of this condition. Most trials that assessed the use of antibiotics in clinical chorioamnionitis included patients with a gestational age of ≥34 weeks and in labor. The first-line antimicrobial regimen for the treatment of clinical chorioamnionitis is ampicillin combined with gentamicin, which should be initiated during the intrapartum period. In the event of a cesarean delivery, patients should receive clindamycin at the time of umbilical cord clamping. The administration of additional antibiotic therapy does not appear to be necessary after vaginal or cesarean delivery. However, if postdelivery antibiotics are prescribed, there is support for the administration of an additional dose. Patients can receive antipyretic agents, mainly acetaminophen, even though there is no clear evidence of their benefits. Current evidence suggests that the administration of antenatal corticosteroids for fetal lung maturation and of magnesium sulfate for fetal neuroprotection to patients with clinical chorioamnionitis between 24 0/7 and 33 6/7 weeks of gestation, and possibly between 23 0/7 and 23 6/7 weeks of gestation, has an overall beneficial effect on the infant. However, delivery should not be delayed to complete the full course of corticosteroids and magnesium sulfate. Once the diagnosis of clinical chorioamnionitis has been established, delivery should be considered, regardless of the gestational age. Vaginal delivery is the safer option and cesarean delivery should be reserved for standard obstetrical indications. The time interval between the diagnosis of clinical chorioamnionitis and delivery is not related to most adverse maternal and neonatal outcomes. Patients may require a higher dose of oxytocin to achieve adequate uterine activity or greater uterine activity to effect a given change in cervical dilation. The benefit of using continuous electronic fetal heart rate monitoring in these patients is unclear. We identified the following promising interventions for the management of clinical chorioamnionitis: (1) an antibiotic regimen including ceftriaxone, clarithromycin, and metronidazole that provides coverage against the most commonly identified microorganisms in patients with clinical chorioamnionitis; (2) vaginal cleansing with antiseptic solutions before cesarean delivery with the aim of decreasing the risk of endometritis and, possibly, postoperative wound infection; and (3) antenatal administration of N-acetylcysteine, an antioxidant and antiinflammatory agent, to reduce neonatal morbidity and mortality. Well-powered randomized controlled trials are needed to assess these interventions in patients with clinical chorioamnionitis.

Prevention and Therapy of Preterm Birth. Guideline of the DGGG, OEGGG and SGGG (S2k Level, AWMF Registry Number 015/025, February 2019) - Part 2 with Recommendations on the Tertiary Prevention of Preterm Birth and the Management of Preterm Premature Rupture of Membranes

Aims This is an official guideline of the German Society for Gynecology and Obstetrics (DGGG), the Austrian Society for Gynecology and Obstetrics (ÖGGG) and the Swiss Society for Gynecology and Obstetrics (SGGG). The aim of this guideline is to improve the prediction, prevention and management of preterm birth based on evidence obtained from recently published scientific literature, the experience of the members of the guideline commission and the views of self-help groups. Methods The members of the participating medical societies and organizations developed Recommendations and Statements based on the international literature. The Recommendations and Statements were adopted following a formal consensus process (structured consensus conference with neutral moderation, voting done in writing using the Delphi method to achieve consensus). Recommendations Part 2 of this short version of the guideline presents Statements and Recommendations on the tertiary prevention of preterm birth and the management of preterm premature rupture of membranes.

A novel molecular microbiologic technique for the rapid diagnosis of microbial invasion of the amniotic cavity and intra-amniotic infection in preterm labor with intact membranes

PROBLEM

The diagnosis of microbial invasion of the amniotic cavity (MIAC) has been traditionally performed using traditional cultivation techniques, which require growth of microorganisms in the laboratory. Shortcomings of culture methods include the time required (days) for identification of microorganisms, and that many microbes involved in the genesis of human diseases are difficult to culture. A novel technique combines broad-range real-time polymerase chain reaction with electrospray ionization time-of-flight mass spectrometry (PCR/ESI-MS) to identify and quantify genomic material from bacteria and viruses.

METHOD OF STUDY

AF samples obtained by transabdominal amniocentesis from 142 women with preterm labor and intact membranes (PTL) were analyzed using cultivation techniques (aerobic, anaerobic, and genital mycoplasmas) as well as PCR/ESI-MS. The prevalence and relative magnitude of intra-amniotic inflammation [AF interleukin 6 (IL-6) concentration ≥ 2.6 ng/mL], acute histologic chorioamnionitis, spontaneous preterm delivery, and perinatal mortality were examined.

RESULTS

(i) The prevalence of MIAC in patients with PTL was 7% using standard cultivation techniques and 12% using PCR/ESI-MS; (ii) seven of ten patients with positive AF culture also had positive PCR/ESI-MS [≥17 genome equivalents per PCR reaction well (GE/well)]; (iii) patients with positive PCR/ESI-MS (≥17 GE/well) and negative AF cultures had significantly higher rates of intra-amniotic inflammation and acute histologic chorioamnionitis, a shorter interval to delivery [median (interquartile range-IQR)], and offspring at higher risk of perinatal mortality, than women with both tests negative [90% (9/10) versus 32% (39/122) OR: 5.6; 95% CI: 1.4-22; (P < 0.001); 70% (7/10) versus 35% (39/112); (P = 0.04); 1 (IQR: <1-2) days versus 25 (IQR: 5-51) days; (P = 0.002), respectively]; (iv) there were no significant differences in these outcomes between patients with positive PCR/ESI-MS (≥17 GE/well) who had negative AF cultures and those with positive AF cultures; and (v) PCR/ESI-MS detected genomic material from viruses in two patients (1.4%).

CONCLUSION

(i) Rapid diagnosis of intra-amniotic infection is possible using PCR/ESI-MS; (ii) the combined use of biomarkers of inflammation and PCR/ESI-MS allows for the identification of specific bacteria and viruses in women with preterm labor and intra-amniotic infection; and (iii) this approach may allow for administration of timely and specific interventions to reduce morbidity attributed to infection-induced preterm birth.

Genital mycoplasmas in placental infections

Objective: The involvement of the genital mycoplasmas Ureaplasma urealyticum and Mycoplasma hominis in complications of pregnancy has remained controversial especially because these microorganisms are frequent colonizers of the lower genital tract. Recovery of bacteria from the placenta appears to be the sole technique to represent a true infection and not vaginal contamination. Therefore, we investigated the presence of genital mycoplasmas, aerobic and anaerobic bacteria, and fungi in human placentas and evaluated their association with morbidity and mortality of pregnancy.

Methods: We cultured placentas from 82 women with complicated pregnancies. One hundred placentas from women with uncomplicated pregnancies were evaluated as controls. When possible, placentas were examined histologically for presence of chorioamnionitis.

Results: Microorganisms were recovered from 52% of the placentas of complicated pregnancies and U. urealyticum was the microorganism isolated most frequently from the placenta. A significant association between positive mycoplasma culture of the placenta and complication of pregnancy was found, and chorioamnionitis was positively related to isolation of mycoplasmas.

Conclusions: These data suggest that genital mycoplasmas are able to infect the human placenta where they can cause chorioamnionitis. This infection of the placenta by genital mycoplasmas is related to preterm birth and fatal outcome of pregnancy.

Microbial interactions in the vaginal ecosystem, with emphasis on the pathogenesis of bacterial vaginosis

During bacterial vaginosis (BV), populations of lactobacilli which are generally dominant in the vagina of overtly healthy women are replaced by other facultative and anaerobic microorganisms. Some Lactobacillus strains produce hydrogen peroxide and all produce lactic acid; however, the antagonistic role of these metabolites in vivo remains controversial. Positive interactions among BV-associated organisms may contribute to the pathogenesis of BV and its sequelae.

Pathophysiology, diagnosis, and management of intraamniotic infection

Intraamniotic infection (IAI) is a term used to describe a clinically diagnosed infection of the contents of the uterus. It is found most often after rupture of the membranes. The most useful diagnostic tests are physical examination, amniotic fluid glucose determination, and amniotic fluid Gram's stain. There is no clearly established means for the prevention of IAI, but cervical examinations and cervical manipulation can increase the risk, so caution with their use is still warranted. Treatment for this infection should be initiated when the diagnosis is made to provide the lowest risk of neonatal and maternal complications. Ampicillin or penicillin plus gentamicin are the most extensively tested antibiotics for treatment before delivery. Clindamycin or metronidazole should be added if a cesarean section is performed. As a general rule, antibiotics should be continued postpartum until the patient has been afebrile and asymptomatic for a minimum of 24 hours. Neonatal complications of IAI may be substantial especially for the premature fetus. Women with this infection have a greater risk for dysfunctional labor and cesarean section.

Chorioamnionitis and endometritis

Chorioamnionitis complicates 1% to 2% of all pregnancies and may affect 10% of women with certain risk factors. Intraamnionic infection may result in devastating morbidity for both the fetus and the mother. Also, chorioamnionitis is associated with higher cesarean section rates. As demonstrated earlier, endometritis is a common complication of cesarean delivery alone. Nevertheless, antibiotic prophylaxis has been shown to reduce postpartum morbidity. In the face of chorioamnionitis and a cesarean delivery, the risk of developing endometritis increases exponentially. However, if appropriate antibiotic therapy is instituted at the time of diagnosis, fetal and maternal outcomes improve dramatically. Similar to chorioamnionitis, endometritis is usually polymicrobial in nature. The preponderance of the organisms isolated are anaerobic. Established risk factors include operative delivery, prolonged ruptured fetal membranes, and prolonged labor. The diagnosis is based primarily on clinical examination with fever and the exclusion of other sources of extrapelvic infection. Once the diagnosis is established, appropriate empiric antibiotics are instituted. Antibiotic therapy should be continued until the patient is afebrile and asymptomatic for 24 to 36 hours. Over the past 20 years, the use of single-agent therapy in these serious infections has been shown to be safe as well as effective. Once successful therapy is completed, the patient is discharged home with no oral antibiotics.

Chorioamnionitis and bacterial vaginosis

An improved understanding of bacterial vaginosis and of clinical intraamniotic infection and histologic chorioamnionitis has produced data showing strong associations among these conditions. It has recently been shown that the microorganisms in both bacterial vaginosis and clinical intraamniotic infection are similar, of which anaerobes, Gardnerella vaginalis, and Mycoplasma hominis are the predominant organisms in both. Furthermore, in the amniotic fluid of women with intraamniotic infection, strong associations among anaerobes, G. vaginalis, and M. hominis have recently been observed. In two epidemiologic studies (one in a high-risk group of women in labor and another in a lower risk group of antepartum women), the presence of bacterial vaginosis has been associated with the development of intraamniotic infection. Additional recent studies have provided new evidence that histologic inflammation of the placental membranes is associated with both clinical intraamniotic infection and positive cultures of the placenta. Multiple logistic regression analysis has shown a relationship between isolation of organisms from the chorioamnion and bacterial vaginosis.

Genital mycoplasmas in preterm infants: prevalence and clinical significance

The genital mycoplasmas: Ureaplasma urealyticum and Mycoplasma hominis have recently assumed an increasing importance as neonatal pathogens. The aim of the present survey was to determine the prevalence of infections with these organisms in preterm infants in two neonatal intensive care units in Israel. Among 99 preterm infants, 24 (24%) harboured mycoplasmas in their throats shortly after birth. U. urealyticum was the most common organism. M. hominis was isolated only from 3 infants. Six out of 27 (22%) mechanically ventilated infants secreted U. urealyticum in their lower airways. The rate of colonization was inversely correlated with gestational age; 80% of infants younger than 28 weeks gestation were found to be colonized as opposed to 17.9% at 28-36 weeks of gestation. No mycoplasmas were isolated in blood cultures drawn from 146 infants and CSF cultures obtained from 47 preterm infants. Neonatal mortality, respiratory complications and intraventricular haemorrhage grade 3-4 were significantly increased in colonized infants. However, above gestational age of 27 weeks, colonization with mycoplasmas was not associated with a worse prognosis. We conclude that colonization with U. urealyticum is common in Israeli preterm infants, correlates inversely with gestational age and has no detrimental effect on neonatal morbidity and mortality of infants older than 27 wks of gestation.

Progress in pathogenesis and management of clinical intraamniotic infection

In the past decade, gratifying progress has been achieved in our understanding of clinical intraamniotic infection. With a usual incidence of 1% to 4%, clinical intraamniotic infection mainly develops as an ascending process after prolonged rupture of the membranes and labor, but other cases may be hematogenous in origin whereas still others complicate intrauterine procedures. The most common organisms isolated in amniotic fluid of cases of intraamniotic infections are anaerobes, genital mycoplasmas, group B streptococci, and Escherichia coli. The latter two are found most commonly in maternal or neonatal bacteremia complicating intraamniotic infection. Although the diagnosis remains largely a clinical one, laboratory tests have been suggested to confirm the diagnosis in women with symptoms. These include amniotic fluid Gram stain, gas-liquid chromatography, and leukocyte esterase measurement. Maternal treatment consists of antibiotic therapy and delivery. Studies to date have used a penicillin plus an aminoglycoside, with some authors advocating the addition of clindamycin after cesarean delivery. Other broad-spectrum regimens may be equally effective. Complications of clinical intraamniotic infections include an increase in cesarean section rate and in maternal and neonatal bacteremia. Poor neonatal outcomes in intraamniotic infection are more likely in the following cases: (1) when E. coli or group B streptococci are present in the amniotic fluid; (2) when the infant has a low birth weight; (3) when maternal antibiotic therapy is delayed until after delivery.

Detection of Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum in pregnant Dutch women

A prospective study was performed to determine the prevalence of endocervical infection by Chlamydia trachomatis and vaginal colonization by Mycoplasma hominis and Ureaplasma urealyticum in pregnant women seeking routine obstetrical care in two clinics in the southern part of the Netherlands. C. trachomatis was detected using the direct immunofluorescence staining technique. For the genital mycoplasmata, generally accepted culture methods were used. Evaluable samples were obtained from 691 of 770 women in the first trimester of pregnancy. C. trachomatis was detected in 2.3%, M. hominis in 5.2% and U. urealyticum in 23.9% of the women. The isolation percentages of C. trachomatis and U. urealyticum were almost equally distributed in the different age groups. The prevalence of all three micro-organisms did not seem to be related to parity. Smoking and alcohol consumption seemed to influence the isolation rate of M. hominis and U. urealyticum.

Postpartum bacteremia and placental colonization with genital mycoplasmas and pregnancy outcome

The influence of placental colonization and postpartum bacteremia with genital mycoplasmas on the course of delivery and the immediate postpartum period was evaluated in 511 women who gave birth to live infants of at least 26 weeks' gestation. Genital mycoplasmas were isolated from the placenta in 153 patients (29.9%) and from blood in four patients (0.8%). These four isolates were all Ureaplasma urealyticum. Patients with genital mycoplasmas isolated from the placenta were delivered of infants with birth weights and gestational ages similar to those of infants of patients who did not have genital mycoplasmas in the placenta (3260 gm and 39.2 weeks versus 3272 gm and 39.3 weeks). No adverse effects of maternal postpartum bacteremia with genital mycoplasmas were observed, either in the mother or in the baby. We conclude that, whereas genital mycoplasmas frequently can be isolated from the placenta, there is no evident relationship between the presence of genital mycoplasmas and pregnancy outcome. In a few instances U. urealyticum has been isolated from the blood of afebrile postpartum women. In these women the presence of this bacteria is probably related to the birth process. This bacteremia does not precede an infectious complication.

Mycoplasma hominis in maternal and fetal infections

Although prevalence of M. hominis colonization during pregnancy varies from 12-50%, its role in infections of the mother and newborn infants is unclear. Definite correlations exist with chorioamnionitis and amniotic fluid infections, but as it is rarely isolated alone during these infections, its pathogenic role is uncertain. Its association with septic abortion is similarly questioned. Prevalence and antibody titers to M. hominis increase with increasing parity. Transient bacteremia occurs in approximately 2.5% of normal deliveries. M. hominis does have a significant role in postpartum fever. Women harboring the organism during labor with low predelivery antibody titers are at risk. Approximately 30% of exposed infants are colonized (4% of all infants) but there are only a few reports of neonatal meningitis, pneumonia, or skin abscesses due to M. hominis. Most recover without specific therapy. The role of antimicrobial therapy of M. hominis in pregnancy and the neonatal period is unclear. Further studies of these issues should simultaneously consider all potential genital tract pathogens.

Postcesarean wound infection by Mycoplasma hominis in a patient with persistent postpartum fever

Mycoplasma hominis was isolated in pure culture from a wound infection following delivery by cesarean section. The importance of recognizing this organism as a potential pathogen of the female genital tract is emphasized. Two commercially available isolation systems that allow the recovery of this organism are also described.

Clinical and microbiologic risk evaluation for post-cesarean section endometritis by multivariate discriminant analysis: role of intraoperative mycoplasma, aerobes, and anaerobes

The clinical and microbiologic risk factors for postpartum endometritis were studied prospectively in 77 patients undergoing cesarean section without antibiotic prophylaxis at Harbor-University of California at Los Angeles Medical Center. Intraoperative cultures were obtained from the amniotic fluid, lower uterine segment, and abdominal wound for isolation of genital mycoplasmas, aerobes, and anaerobes. Postsection endometritis developed in 21 (27%) patients and was significantly associated with presence of either high-virulence bacteria (predominantly, coliforms, streptococci, anaerobic cocci, and bacteroides) (35% to 60% versus 10% to 24%; p less than 0.05) or Ureaplasma urealyticum (15% to 42% versus 0% to 10%; p less than 0.05) at any site compared with afebrile women. Multivariate analysis identified primary cesarean section, younger maternal age, presence of ruptured membranes, and presence of Ureaplasma as significant risk factors independent of other confounding variables (p less than 0.01). It is suggested that genital mycoplasmas could play a primary role in some cases of postsection endometritis or that they are cofactors or markers for the presence of other high-virulence aerobic and anaerobic bacteria.

Isolation of Mycoplasma species and Ureaplasma urealyticum from obstetrical and gynecological patients by using commercially available medium formulations

One hundred duplicate endocervical specimens from obstetrical and gynecological patients were cultured for Mycoplasma spp. and Ureaplasma urealyticum. Rates of recovery of these organisms from commercially prepared A7 medium and the Mycotrim-GU system were compared. We detected 14 (93%) of the total 15 isolates of Mycoplasma spp. on A7 plates and 11 (73%) in the Mycotrim-GU system. We detected 34 (89%) of the total 38 isolates of U. urealyticum on A7 plates and 32 (84%) in the Mycotrim-GU system. The times of detection for both types of organism were similar in the two systems. We conclude that cultivation on A7 medium as described is a more cost-effective method of recovery of Mycoplasma spp. and U. urealyticum than the Mycotrim-GU system.

Further studies on genital mycoplasmas in intra-amniotic infection: blood cultures and serologic response

Mycoplasma hominis is recovered significantly more often in amniotic fluid of women with intra-amniotic infection than in matched control women, but Ureaplasma urealyticum is found in 50% of amniotic fluid samples of both groups. To gain further understanding, we performed blood cultures for genital mycoplasmas and measured serologic responses by a micro enzyme-linked immunosorbent assay method in women with intra-amniotic infection and in control subjects. In blood cultures of 81 women with intra-amniotic infection, M. hominis was isolated in two (2.5%) and U. urealyticum in 11 (13.6%). In 44 control blood cultures, M. hominis was not isolated, and U. urealyticum was recovered in eight (18.2%). These differences were not significant. Serologic response was determined in 86 patients. Rise in antibody to M. hominis was significantly more common in women with intra-amniotic infection and M. hominis in the amniotic fluid than in either women with intra-amniotic infection or control patients without M. hominis. For U. urealyticum antibody response was significantly more common in the intra-amniotic infection group than in control subjects, but there was no association between antibody response and isolation of this organism in amniotic fluid. When M. hominis was found in amniotic fluid or maternal blood, patients were nearly always symptomatic. The high likelihood of serologic response in these cases supports a pathogenic role of M. hominis in intra-amniotic infection. The role of U. urealyticum remains unclear.

Sperm washing and swim-up technique using antibiotics removes microbes from human semen

Pelvic infections may follow intrauterine or intratubal insemination with washed semen. In this study, we determined whether sperm washing removes microorganisms from human semen. Before and after semen wash, we cultured 15 ejaculates for aerobic and anaerobic bacteria, genital mycoplasma, and chlamydia. All semen samples had from one to five organisms isolated (total, 40 isolates) before the semen wash preparation. The mean number (+/- standard deviation) of isolates per sample was 2.67 +/- 1.35. After the semen were prepared, none of the samples showed a positive culture. The decrease in the number of samples with positive cultures and the decrease in the number of isolates is significant (P less than 0.0001). After sperm washing, electronmicroscopic studies did not show any microbes attached to any portion of the spermatozoa. We conclude that the method of sperm wash preparation used is effective in removing microbes present in human semen.

Asymptomatic parturient women with high-virulence bacteria in the amniotic fluid

This study describes the postpartum course of asymptomatic parturient women who had greater than or equal to 10(2) cfu of high-virulence (HV) bacteria per milliliter of amniotic fluid. Of 60 asymptomatic parturient women with greater than or equal to 10(2) cfu of HV bacteria per milliliter of amniotic fluid, 27 (48%) remained asymptomatic in the puerperium, 16 (27%) developed fever only, and 17 (28%) developed endometritis. In asymptomatic versus symptomatic women, there were no statistically significant differences in number or type of isolates or in length of membrane rupture or labor-to-collection interval. However, there were significant differences in the intervals from collection to delivery and in the rate of cesarean section delivery. For comparison, 40 of these patients were matched with women in whom only low-virulence organisms were detected in the amniotic fluid. In the HV group, 16 women (40%) remained asymptomatic, 15 (37.5%) developed fever only, and nine (22.5%) had endometritis. In the low-virulence group, 27 women (67.5%) remained asymptomatic, 10 (25%) developed fever only, one (2.5%) developed endometritis 10 days post partum, and two (5%) had other infections (p less than 0.01). Clinically evident uterine infection depends upon type and numbers of bacteria in utero, duration of bacteria in utero, and route of delivery.