Association between bacterial vaginosis and preterm delivery of a low-birth-weight infant. The Vaginal Infections and Prematurity Study Group

BACKGROUND

Bacterial vaginosis is believed to be a risk factor for preterm delivery. We undertook a study of the association between bacterial vaginosis and the preterm delivery of infants with low birth weight after accounting for other known risk factors.

METHODS

In this cohort study, we enrolled 10,397 pregnant women from seven medical centers who had no known medical risk factors for preterm delivery. At 23 to 26 weeks' gestation, bacterial vaginosis was determined to be present or absent on the basis of the vaginal pH and the results of Gram's staining. The principal outcome variable was the delivery at less than 37 weeks' gestation of an infant with a birth weight below 2500 g.

RESULTS

Bacterial vaginosis was detected in 16 percent of the 10,397 women. The women with bacterial vaginosis were more likely to be unmarried, to be black, to have low incomes, and to have previously delivered low-birth-weight infants. In a multivariate analysis, the presence of bacterial vaginosis was related to preterm delivery of a low-birth-weight infant (odds ratio, 1.4; 95 percent confidence interval, 1.1 to 1.8). Other risk factors that were significantly associated with such a delivery in this population were the previous delivery of a low-birth-weight infant (odds ratio, 6.2; 95 percent confidence interval, 4.6 to 8.4), the loss of an earlier pregnancy (odds ratio, 1.7; 1.3 to 2.2), primigravidity (odds ratio, 1.6; 1.1 to 1.9), smoking (odds ratio, 1.4; 1.1 to 1.7); and black race (odds ratio, 1.4; 1.1 to 1.7). Among women with bacterial vaginosis, the highest risk of preterm delivery of a low-birth-weight infant was found among those with both vaginal bacteroides and Mycoplasma hominis (odds ratio, 2.1; 95 percent confidence interval, 1.5 to 3.0).

CONCLUSIONS

Bacterial vaginosis was associated with the preterm delivery of low-birth-weight infants independently of other recognized risk factors.

A review of premature birth and subclinical infection

Premature birth causes high rates of neonatal morbidity and mortality. There are multiple causes of preterm birth. This article reviews the evidence linking subclinical infection and premature birth. Although maternal genital tract colonization with specific organisms has been inconsistently associated with preterm birth and/or premature rupture of membranes, some infections have been consistently associated with preterm delivery. The association of histologic chorioamnionitis with prematurity is a consistent finding, but the mechanisms require further study. The relationship between histologic chorioamnionitis infection and the chorioamnionitis of prematurity requires additional research. A varying number of patients in "idiopathic" preterm labor have positive amniotic fluid cultures (0% to 30%), but it is not clear whether infection preceded labor or occurred as a result of labor. Evidence of subclinical infection as a cause of preterm labor is raised by finding elevated maternal serum C-reactive protein and abnormal amniotic fluid organic acid levels in some patients in preterm labor. Biochemical mechanisms for preterm labor in the setting of infection are suggested by both in vitro and in vivo studies of prostaglandins and their metabolites, endotoxin and cytokines. Some, but by no means all, antibiotic trials conducted to date have reported decreases in prematurity. These results support the hypothesis that premature birth results in part from infection caused by genital tract bacteria. In the next few years, research efforts must be prioritized to determine the role of infection and the appropriate prevention of this cause of prematurity.

Trichomonas vaginalis associated with low birth weight and preterm delivery. The Vaginal Infections and Prematurity Study Group

BACKGROUND

Several studies have suggested that pregnant women infected with Trichomonas vaginalis may be at increased risk of an adverse outcome.

GOAL

To evaluate prospectively the association between T. vaginalis and risk of adverse pregnancy outcome in a large cohort of ethnically diverse women.

STUDY DESIGN

At University-affiliated hospitals and antepartum clinics in five United States cities, 13,816 women (5,241 black, 4,226 Hispanic, and 4,349 white women) were enrolled at mid-gestation, tested for T. vaginalis by culture, and followed up until delivery.

RESULTS

The prevalence of T. vaginalis infection at enrollment was 12.6%. Race-specific prevalence rates were 22.8% for black, 6.6% for Hispanic, and 6.1% for white women. After multivariate analysis, vaginal infection with T. vaginalis at mid-gestation was significantly associated with low birth weight (odds ratio 1.3; 95% confidence interval 1.1 to 1.5), preterm delivery (odds ratio 1.3; 95% confidence interval 1.1 to 1.4), and preterm delivery of a low birth weight infant (odds ratio 1.4; 95% confidence interval 1.1 to 1.6). The attributable risk of T. vaginalis infection associated with low birth weight weight in blacks was 11% compared with 1.6% in Hispanics and 1.5% in whites.

CONCLUSIONS

After considering other recognized risk factors including co-infections, pregnant women infected with T. vaginalis at mid-gestation were statistically significantly more likely to have a low birth weight infant, to deliver preterm, and to have a preterm low birth weight infant. Compared with whites and Hispanics, T. vaginalis infection accounts for a disproportionately larger share of the low birth weight rate in blacks.

Quantitative bacteriology of amniotic fluid from women with clinical intraamniotic infection at term

Amniotic fluid was collected through an intrauterine catheter from 52 women with clinical intraamniotic infection and from 52 uninfected matched control women. The amniotic fluid was cultured quantitatively for anaerobes and aerobes. Patients with intraamniotic infection were matched with the control women on the basis of gestational age, interval from membrane rupture to specimen collection, and interval from membrane rupture to delivery. The patients with intraamniotic infection had a significantly higher mean temperature (38.4 vs. 37.1 C) and a higher mean leukocyte count (15,740 vs. 11,740 cells/mm3). In 80.6% of specimens from the women with intraamniotic infection and 30.8% of those from the control subjects, greater than or equal to 10(2) colony-forming units (cfu)/ml were isolated from the amniotic fluid (P less than 0.001). Also, in 69.2% of the former and 7.7% of the latter, there were greater than or equal to 10(2) cfu of isolates considered to be "high-virulence" isolates/ml (P less than 0.001).

Risk factors for preterm premature rupture of fetal membranes: a multicenter case-control study

To assess the association between women with preterm premature rupture of membranes and 41 potential risk factors, we conducted a case-control study in six United States tertiary perinatal centers. The study involved completion of a comprehensive questionnaire for 341 women with preterm premature rupture of membranes in singleton pregnancies from 20 to 36 weeks' gestation and 253 control women matched for maternal age, gestational age, parity, clinic or private patient status, and previous vaginal or cesarean delivery. Univariate analysis revealed 11 variables associated with a significantly (p less than 0.05) increased risk of preterm premature rupture of membranes. After multiple logistic regression analysis, three variables remained in the model as independent risk factors: antepartum vaginal bleeding in more than one trimester (odds ratio 7.4; 95% confidence interval, 2.2, 25.6), current cigarette smoking (odds ratio, 2.1; 95% confidence interval, 1.4, 3.1), and previous preterm delivery (odds ratio, 2.5; 95% confidence interval, 1.4, 2.5). Cessation of cigarette smoking by pregnant women may reduce the risk of preterm premature rupture of membranes. Further study is necessary to determine the nature of the relationship between antepartum vaginal bleeding and preterm premature rupture of membranes.

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.

Colonization with group B streptococci in pregnancy and adverse outcome. VIP Study Group

OBJECTIVE

Our purpose was to study the association of cervicovaginal colonization with group B streptococci with pregnancy and neonatal outcome.

STUDY DESIGN

A prospective study was conducted at seven medical centers between 1984 and 1989. Genital tract cultures were obtained at 23 to 26 weeks' gestation and at delivery. Prematurity and neonatal sepsis rates were compared between group B streptococci positive and negative women.

RESULTS

Group B streptococci was recovered from 2877 (21%) of 13,646 women at enrollment. Heavy colonization was associated with a significant risk of delivering a preterm infant who had a low birth weight (odds ratio = 1.5, 95% confidence interval 1.1 to 1.9). Heavily colonized women given antibiotics effective against group B streptococci had little increased risk of a preterm, low-birth-weight birth. Women with light colonization were at the same risk of adverse outcome as the uncolonized women. Neonatal group B streptococci sepsis occurred in 2.6 of 1000 live births in women with and 1.6 of 1000 live births in women without group B streptococci at 23 to 26 weeks' gestation (p = 0.11). However, sepsis occurred in 16 of 1000 live births to women with and 0.4 of 1000 live births to women without group B streptococci at delivery (p < 0.001).

CONCLUSIONS

Heavy group B streptococci colonization of 23 to 26 weeks' gestation was associated with an increased risk of delivering a preterm, low-birth-weight infant. Cervicovaginal colonization with group B streptococci at 23 to 26 weeks' gestation was not a reliable predictor of neonatal group B streptococci sepsis. Colonization at delivery was associated with sepsis.

Characteristics of three vaginal flora patterns assessed by gram stain among pregnant women. Vaginal Infections and Prematurity Study Group

This study was undertaken to define the characteristics and persistence of vaginal flora in 7918 pregnant women at 23 to 26 weeks' gestation. Vaginal smears were categorized as normal (predominant lactobacilli), intermediate (reduced lactobacilli), or positive for bacterial vaginosis. The women with normal flora were least likely to have elevated vaginal pH, amine odor, milky discharge, or colonization by Gardnerella, Bacteroides, or genital mycoplasmas. Women with intermediate vaginal flora had intermediate frequencies of these clinical signs and microorganisms. Group B streptococci and yeast were associated with normal or intermediate flora, whereas Neisseria gonorrhoeae and Chlamydia trachomatis were recovered more frequently from women with intermediate flora or bacterial vaginosis. Trichomonas vaginalis was most associated with intermediate flora. At follow-up, 81% of the women with normal flora had remained normal. Of the women with intermediate flora, 32% acquired bacterial vaginosis and 30% shifted to normal flora. Only 12% of the women with bacterial vaginosis had shifted to normal flora. We conclude that there are two primary stable vaginal flora patterns (normal flora or bacterial vaginosis) and a third less distinct transitional flora pattern between these two.

A randomized placebo-controlled trial of erythromycin for the treatment of Ureaplasma urealyticum to prevent premature delivery. The Vaginal Infections and Prematurity Study Group

Ureaplasma urealyticum has been associated with low birth weight and histologic chorioamnionitis and it is a frequent isolate from the chorioamnion of patients who are delivered prematurely. In prior clinical trials using antibiotics active against U. urealyticum, antibiotic treatment was associated with reduced prematurity and increased mean birth weight. In this multicenter, randomized, double-blind clinical trial, pregnant women with U. urealyticum were treated with 333 mg of erythromycin base or placebo three times daily, starting between 26 and 30 weeks' gestation and continuing through 35 completed weeks of pregnancy. Women with urinary tract infection or Neisseria gonorrhoeae infection were excluded from the trial, and women with Chlamydia trachomatis or group B streptococci were excluded from these analyses. Erythromycin did not eliminate U. urealyticum from the lower genital tract. There were no significant differences between erythromycin- and placebo-treated women in infant birth weight or gestational age at delivery, in frequency of premature rupture of membranes, or in neonatal outcome.

A randomized trial of intrapartum versus immediate postpartum treatment of women with intra-amniotic infection

A randomized trial of intrapartum versus postpartum antibiotic treatment of women with intra-amniotic infection was conducted. Intra-amniotic infection was treated with ampicillin and gentamicin during labor (at the time of diagnosis) in 26 women and immediately after umbilical cord clamping in 19 women. Intrapartum treatment led to a lower incidence of neonatal sepsis (0 versus 21%; P = .03) and a shorter neonatal hospital stay (3.8 versus 5.7 days; P = .02) when compared with postpartum treatment. There were no significant differences in the microbiologic results, the gestational age, or the birth weight between the groups. Intrapartum-treated mothers had a shorter mean postpartum stay, a lower mean number of febrile days, and a lower mean peak postpartum temperature than did postpartum-treated mothers; these differences were all statistically significant (P = .05). The treatment of clinical intra-amniotic infection during labor results in improved outcome.

Evidence relating bacterial vaginosis to intraamniotic infection

We performed a two-part study to determine relationships of bacterial vaginosis and intraamniotic infection. In the first part of the study, we determined whether bacterial vaginosis organisms (Gardnerella vaginalis, Mycoplasma hominis, and anaerobes) were associated with each other in the amniotic fluid of 408 cases of intraamniotic infection. In the second part, we determined the association of bacterial vaginosis itself with intraamniotic infection in 125 cases at high risk for intraamniotic infection. Strong associations were observed among the bacterial vaginosis organisms in amniotic fluid (p less than 0.01 to p less than 0.001). Women with bacterial vaginosis were more likely to develop intraamniotic infection than those without bacterial vaginosis (69% vs. 46%, p = 0.03). Women with bacterial vaginosis were more likely to have G. vaginalis and M. hominis in the amniotic fluid (p less than 0.01 and 0.04, respectively). These observations implicate bacterial vaginosis as a cause of intraamniotic infection.

Epidemiology and outcomes associated with moderate to heavy Candida colonization during pregnancy. Vaginal Infections and Prematurity Study Group

OBJECTIVE

Our purpose was to determine the risk factors, physical findings, microflora, and pregnancy outcome among pregnant women with moderate to heavy vaginal growth of Candida albicans and other Candida species.

STUDY DESIGN

A multicenter cohort of 13,914 women were enrolled between 23 and 26 weeks' gestation. Women completed a questionnaire, underwent a physical examination, and had genital specimens taken for culture. A subset of 1459 women were reexamined during the third trimester. Pregnancy outcomes were recorded at delivery.

RESULTS

The prevalence of moderate to heavy Candida colonization at midgestation was 10%. Colonized women, 83% of whom carried C. albicans, were more likely to be black or Hispanic, unmarried, a previous oral contraceptive user, and to manifest clinical signs indicative of Candida carriage. Candida colonization was positively associated with Trichomonas vaginalis, group B streptococci, and aerobic Lactobacillus and was not associated with adverse pregnancy outcome.

CONCLUSION

These results suggest that Candida colonization is not associated with low birth weight or preterm delivery.

Clinical risk factors for puerperal infection

Recent studies have identified clinical features that are major risk factors for puerperal infection. Patients of low socioeconomic status undergoing cesarean section who have had prolonged labor and rupture of membranes (ROM) incur a 40 to 85% risk of endometritis. Infection occurs generally in less than 10% of women undergoing vaginal delivery, even when complicated by prolonged ROM, and often in considerably fewer cases. Other features such as internal monitoring, obesity, anemia, and general anesthesia have not been consistent determinants in recent studies.

Immunization of pregnant women with influenza A/New Jersey/76 virus vaccine: reactogenicity and immunogenicity in mother and infant

The safety and immunogenicity of inactivated influenza virus vaccines in pregnant women have not been adequately investigated. In this study, 56 women received inactivated influenza A/New Jersey/76 virus vaccine during the second and third trimesters of pregnancy. No significant immediate reactions or increased fetal complications were associated with administration of the vaccine. The antibody response of the pregnant women to the vaccine was similar to that of nonpregnant adults. Forty mother-infant pairs were available for antibody surveillance. At delivery, reciprocal antibody titers of greater than or equal to 20 were present in 11 (42%) newborn (cord) sera and 15 (58%) maternal sera. Three months later, sera from only three infants (12%) contained this level of antibody. At six months, the serum of only one infant contained this level of antibody. At six months, the serum of only one infant contained detectable antibodies. Levels of passively transferred antibodies from prior maternal infection with influenza A/Victoria/75 virus also declined rapidly following birth. It is possible that immunization of pregnant women can provide sufficient protection of the newborn infants by transfer of antibodies through the placenta if (1) a more potent influenza vaccine, possibly used with booster dosing, is administered, and (2) the women deliver just prior to or during the influenza season.

Management of acute chorioamnionitis

Acute chorioamnionitis has been recognized as a major threat to both mother and fetus, but there has been little study of its therapy. On this service, the plan of management consists of parenteral, broad-spectrum antibiotic therapy and prompt action to effect delivery. Cesarean section was generally performed only when there were additional obstetric indications. No arbitrary time limit was set for the diagnosis-to-delivery interval. The perinatal mortality rate was increased fourfold, but few deaths could be attributed to infection. Maternal outcome was usually good following vaginal delivery and more complicated following abdominal delivery. Over 90% of patients were delivered within 12 hours of diagnosis of chorioamnionitis.

The relationship between infections and adverse pregnancy outcomes: an overview

Preterm birth with its subsequent morbidity and mortality is the leading perinatal problem in the United States. Infants born before the thirty-seventh week of gestation account for approximately 6% to 9% of all births, but 70% of all perinatal deaths and half of all long-term neurologic morbidity. Current approaches focus on symptomatic treatment. Despite widespread use of drugs to arrest preterm labor (tocolytics), there has been no decrease in low birth weight or preterm infants in the last 20 years. It is likely that therapy directed at preventing or treating underlying causes would be more successful. Evidence from many sources links preterm birth to symptomatic infections, for example, of the urinary or respiratory tracts. In the last decade, great interest has been generated to support the hypothesis that subclinical infection is an important cause of preterm labor. Evidence to support this may be categorized as follows: histological chorioamnionitis is increased in preterm births; clinical infection is increased after preterm birth; there is significant association of some lower genital tract organisms and infections with preterm birth or preterm premature rupture of the membranes; there are positive cultures of amniotic fluid or membranes from some patients with preterm labor and preterm birth; there are markers of infections in preterm birth; bacteria or their products induce preterm birth in animal models; and some antibiotic trials have shown a lower rate of preterm birth or have deferred preterm birth. In the last 5 years, additional exciting information has suggested that not only is subclinical infection responsible for preterm birth but also many serious neonatal sequelae including periventricular leukomalacia, cerebral palsy, respiratory distress, and even bronchopulmonary dysplasia and necrotizing enterocolitis. In sum, a large body of clinical and laboratory information suggests that subclinical infection is a major cause of preterm birth, especially those occurring before 30 weeks. This concept holds promise that new approaches can be developed to prevent prematurity.

The genital flora of women with intraamniotic infection. Vaginal Infection and Prematurity Study Group

The relationship of genital flora assessed at the end of the second trimester of pregnancy and intraamniotic infection diagnosed by clinical signs and symptoms during labor was evaluated. Women were enrolled at 23-26 weeks of gestation and followed through delivery in the multi-center Vaginal Infections and Prematurity Study (1984-1989). Among the cohort of 11,989 followed through delivery, 286 (2.4%) developed intraamniotic infection. The recovery of Gardnerella vaginalis (relative risk [RR] = 1.8; 95% confidence interval [CI] = 1.4-2.4), heavy growth of Bacteroides species (RR = 1.5; 95% CI = 1.1-2.1), and isolation of Mycoplasma hominis (RR = 1.7; 95% CI = 1.3-2.1) from the vagina at the end of the second trimester of pregnancy were associated with an increased risk of intraamniotic infection. Bacterial vaginosis was also associated with intraamniotic infection (RR = 1.5; 95% CI = 1.1-2.2). These findings extend prior studies by showing that prenatal cultures for microorganisms associated with bacterial vaginosis predicted an increased risk of intraamniotic infection.

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.

Intraamniotic infection in low-birth-weight infants

Intraamniotic infection (IAI) complicating births of low-birth-weight infants (less than 2500 g) was compared with IAI in births of infants weighing greater than or equal to 2500 g for differences in neonatal and maternal infectious morbidity and mortality, as well as differences in microbiological isolates in amniotic fluid. Four hundred four cases of clinically diagnosed IAI were prospectively evaluated. Thirty-seven patients (9.2%) delivered neonates less than 2500 g, and 367 patients (90.8%) delivered neonates greater than or equal to 2500 g. The low-birth-weight group had a significant increase in the incidence of sepsis (16.2% vs. 4.1%, P = .005) and death from sepsis (10.8% vs. 0%, P less than .001). Additional intrapartum conditions that might further predispose the low-birth-weight group to an increased risk of sepsis were not evident. Evaluation of the amniotic fluid did not demonstrate any increase in prevalence of group B streptococci, Escherichia coli, or enterococci in the low-birth-weight group. The presence of gram-negative anaerobes was significantly increased, however, in low-birth-weight pregnancies with IAI (59.5% vs. 31.6%, P = .001).

Amniotic fluid tumor necrosis factor-alpha and interleukin-1 in a rabbit model of bacterially induced preterm pregnancy loss

OBJECTIVE

The objective of this study was to determine whether the cytokines tumor necrosis factor-alpha, interleukin-1 alpha, and interleukin-1 beta were produced in the amniotic fluid of the rabbit after intracervical inoculation with Escherichia coli.

STUDY DESIGN

Timed pregnant rabbits on day 21 (70% of gestation) were inoculated with a hysteroscope intracervically with 10(4) to 10(5) colony-forming units Escherichia coli or sterile saline solution. Escherichia coli-inoculated animals (N = 16) were put to death at 4, 8, 12, and 16 hours after inoculation. Control animals (N = 6) were put to death at similar intervals. At death, cultures were taken from endometrium, amniotic fluid, peritoneum, and blood. Amniotic fluid was collected and assayed for tumor necrosis factor bioactivity by a modified fibroblast cytotoxic assay in L929 cells, for interleukin-1 alpha, and interleukin-1 beta with a specific radioimmunoassay, and for prostaglandin E2 and prostaglandin F2 alpha by radioimmunoassay.

RESULTS

Levels of amniotic fluid tumor necrosis factor-alpha, interleukin-1 alpha, and interleukin-1 beta were elevated as early as 4 hours after inoculation in some animals and by 12 to 16 hours after inoculation in all. Levels of all three cytokines correlated significantly with time from intracervical inoculation with Escherichia coli (p < 0.05). Levels of amniotic fluid prostaglandin E2 and prostaglandin F2 alpha correlated significantly with time from intracervical inoculation with Escherichia coli (p < 0.05).

CONCLUSIONS

Levels of tumor necrosis factor-alpha, interleukin-1 alpha, interleukin-1 beta, prostaglandin E2 and prostaglandin F2 alpha are elevated in the amniotic fluid of rabbits after intracervical inoculation with Escherichia coli. Similarity exists between elevations of amniotic fluid cytokines in this model and in cases of intraamniotic infection and preterm labor unresponsive to tocolytics in humans. Modulation of cytokines may offer a strategy for improvement of outcome in this experimental model of infection-induced pregnancy loss.

Outcome of the Vaginal Infections and Prematurity Study: results of a clinical trial of erythromycin among pregnant women colonized with group B streptococci

OBJECTIVE

Our purpose was to determine whether erythromycin treatment of pregnant women colonized with group B streptococci would reduce the occurrence of low birth weight (< 2500 gm) and preterm (< 37 completed weeks) birth.

STUDY DESIGN

In a double-blind clinical trial, 938 carriers of group B streptococci were randomized to receive erythromycin base (333 mg three times a day) or matching placebo beginning during the third trimester and before 30 weeks and continuing for 10 weeks or until 35 weeks 6 days of pregnancy.

RESULTS

Pregnancy outcomes were available for 97% of randomized women; 14% of subjects withdrew from the trial. Birth weight < 2500 gm occurred in 8.6% of the erythromycin and 6.1% of the placebo recipients (relative risk 1.4, 0.9 to 2.2, p = 0.16). Preterm delivery occurred in 11.4% of women randomized to erythromycin and in 12.3% randomized to placebo (relative risk 0.9, 95% confidence limits 0.6 to 1.3, p = 0.65). Greater benefit of erythromycin in reducing these outcomes was not observed among women reporting the best compliance.

CONCLUSIONS

In this study of pregnant women colonized with group B streptococci treatment with erythromycin was not shown to be effective at prolonging gestation or reducing low birth weight. Greater than anticipated complicating factors, including spontaneous clearance of the organism, use of nontrial antibiotics, and density of colonization, may have resulted in population sizes too small to detect a benefit of treatment. Future studies should take these factors into account in determining sample sizes.

A prospective, controlled study of maternal and perinatal outcome after intra-amniotic infection at term

A study was made of the outcome for mothers and their neonates with both clinical and bacteriologic evidence of intra-amniotic infection at term. Samples of amniotic fluid from patients with intra-amniotic infection showed greater than 10(2) colony-forming units per milliliter of a high-virulence isolate, whereas samples from control patients showed no growth or low-virulence isolates only. Control patients were uninfected during labor and were matched on the basis of gestational age, interval from rupture of membranes to delivery, and mode of delivery. There were 67 matched pairs. The mean interval from diagnosis of intra-amniotic infection to delivery was 3.1 +/- 2.2 hours (+/- SD). Mothers with intra-amniotic infection had a significantly longer hospital stay and greater fever index after delivery than did control patients. Intrapartum bacteremia was documented in six of 50 (12%) women with intra-amniotic infection. The cesarean birth rate was 36%. There was one case of probable septic shock and one of postpartum hemorrhage among women with intra-amniotic infection. Infants in the intra-amniotic infection group had a significantly longer hospital stay than did the control infants. Among 59 infants for whom blood culture results were available, bacteremia was documented in five (8%) with intra-amniotic infection. Definite radiographic evidence of pneumonia was present in 4%; there were no cases of meningitis. There was one perinatal death in the intra-amniotic infection group. Overall, the maternal and perinatal outcome after intra-amniotic infection at term was excellent.

A rabbit model for bacteria-induced preterm pregnancy loss

Bacterial infection has been implicated in premature labor in humans. To elucidate mechanisms and potential intervention strategies, we sought to develop a model of infection-induced pregnancy loss in rabbits. On day 21 (70% of gestation), each uterine horn was inoculated hysteroscopically with 0.2 ml containing saline solution of 10(6) cfu Escherichia coli or Bacteroides bivius or Fusobacterium necrophorum. Fetal viability was assessed. Animals were sacrificed at various times or as delivery occurred. Serum progesterone and amniotic fluid prostaglandins were measured. Cultures and histologic sections were prepared. Compared with the saline solution group, E coli and F. necrophorum-inoculated rabbits were significantly more likely to deliver (16 of 16 and six of seven with mean times of 31.9 +/- 10.7 and 28.3 +/- 11.5 hours, respectively for E. coli and F. necrophorum). Positive amniotic fluid cultures for the E. coli group were found in 11 of 12 (92%) and for the F. necrophorum group in three of three cases (100%). Histologic inflammation was seen heavily in both the E. coli and F. necrophorum groups, whereas it was absent in the saline solution group. Inoculation with B. bivius led to a much lower pregnancy loss rate (eight of 32) and less histologic inflammation despite positive uterine cultures in most animals. This model may provide an opportunity to determine mechanisms of clinical or subclinical intraamniotic infection and to test intervention strategies.

Placental transfer of clindamycin and gentamicin in term pregnancy

The pharmacokinetics of clindamycin and gentamicin were studied in women given these antibiotics prior to cesarean section. Maternal clindamycin levels were within the normal range and cord levels were within the therapeutic range for this antibiotic. For gentamicin, however, maternal levels were depressed, with a concurrent depression of cord levels. This may have significant implications for the use of gentamicin in maternal and fetomaternal infections.

The interrelationship of complement-activation fragments and angiogenesis-related factors in early pregnancy and their association with pre-eclampsia

OBJECTIVE

To determine the interrelationships during early pregnancy of complement-activation fragments Bb, C3a and sC5b-9, and angiogenesis-related factors placental growth factor (PiGF), soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), and their associations with pre-eclampsia.

DESIGN

Prospective cohort study.

SETTING

Denver complement study (June 2005-June 2008).

POPULATION

A total of 668 pregnant women with singleton gestations, recruited between 10 and 15 weeks of gestation.

METHODS

Using univariable and multivariable logistic regression analysis, concentrations of complement-activation fragments and angiogenesis-related factors were compared between 10 and 15 weeks of gestation in women who subsequently did or did not develop pre-eclampsia. Interrelationships between these variables were tested using the non-parametric Spearman rank correlation coefficient.

MAIN OUTCOME MEASURE

Pre-eclampsia. The association of complement-activation fragments and angiogenesis-related factors with obesity was also examined.

RESULTS

The mean (+/-SD) levels of complement Bb in early pregnancy among women who did and did not develop pre-eclampsia were 0.84 (+/-0.26) microg/ml and 0.69 (+/-0.2) microg/ml, respectively (P = 0.001). Concentrations of PiGF were significantly (P = 0.01) lower (31 +/- 12 pg/ml) in early pregnancy in the pre-eclamptic group of women, as compared with the normotensive group (39 +/- 32 pg/ml). The adjusted odds ratio (AOR) of Bb and PiGF were 2.1 (CI = 1.4-3.1, P < 0.0003) and 0.2 (CI = 0.07-0.7, P = 0.01), respectively. There was no significant difference in the levels of C3a, sC5b-9, sFlt-1 and sEng in early pregnancy among women who developed pre-eclampsia, compared with women who remained normotensive during pregnancy. Higher levels of Bb (P = 0.0001) and C3a (P = 0.03), and lower levels of sFlt-1 (P = 0.0002) and sEng (P = 0.0001) were found among women with obesity, compared with non-obese controls. No meaningful relationships were found between the complement-activation fragments and the angiogenesis-related factors.

CONCLUSIONS

In this cohort during early pregnancy, increased concentrations of complement-activation factor Bb and lower concentrations of PiGF were associated with the development of pre-eclampsia later in pregnancy.