Prolactin concentrations in preterm and term pregnancy and labour

Maternal plasma and amniotic fluid (AF) were obtained for measurement of prolactin concentrations from: 1) 20 patients with preterm labor and intact membranes who delivered within one week of amniocentesis; 2) 20 patients with preterm labor who responded to tocolysis and delivered at term; 3) 20 women at term who were not in labor and 4) from 20 women in active labor at term. No significant differences were found between: 1) maternal plasma prolactin concentrations in women with preterm labor who delivered prematurely and those who delivered at term (155 ng/ml vs 176.5 ng/ml); 2) patients at term who were not in labor (188 ng/ml) and those who were in labor (155 ng/ml); 3) AF prolactin concentrations in the two preterm labor groups (1987.5 vs 1282.5 ng/ml) and 4) AF prolactin concentration in the two term groups (562 ng/ml vs 701 ng/ml). Prolactin concentrations were generally significantly higher preterm than at term. We concluded that no significant changes in maternal plasma and amniotic fluid prolactin levels were found in preterm and term parturition.     

Amniotic fluid interleukin-18 at mid-trimester genetic amniocentesis: relationship to intraamniotic microbial invasion and preterm delivery

Objective  To determine the value of amniotic fluid interleukin-18 (AF IL-18) in the diagnosis of microbial invasion of the amniotic cavity and prediction of preterm delivery (PTD).
Design  Analysis of the results of AF collected prospectively following genetic amniocentesis between February 2006 and September 2007.
Setting  A tertiary referral centre for fetal medicine.
Methods  Following amniocentesis, a sample of amniotic fluid was transferred to the laboratory for aerobic and anaerobic bacterial cultures, Ureaplasma urealyticum culture and IL-18 assays. All women who delivered preterm (<37 weeks of gestation) formed the study group. The control group consisted of the two subsequent women who also underwent amniocentesis during the same time period and delivered a normal neonate at term, matched for maternal age, parity and indication for amniocentesis.
Main outcome measures  The relationship between AF IL-18 levels and the risk of both microbial invasion of the amniotic cavity and PTD.
Results  Forty-eight women who delivered preterm (<37 weeks) were matched with 96 controls. The preterm delivery group had significantly higher concentrations of IL-18 (median = 609 pg/ml, interquartile range: 445.7–782.7) compared to controls (median = 322.1 pg/ml, interquartile range: 277.7–414.4), ( P  < 0.001). IL-18 level was also significantly higher ( P  < 0.001) in cases with positive amniotic fluid cultures (median = 697.7, interquartile range: 609.0–847.2) compared to those with negative ones (median = 330.9 pg/ml, interquartile range: 235.2–440.8).
Conclusions  Elevated mid-trimester concentrations of AF IL-18 can identify women at risk for intraamniotic infection and spontaneous PTD.     

Cytokine abundance in placental tissues: evidence of inflammatory activation in gestational membranes with term and preterm parturition

OBJECTIVES: This study of the changes in cytokine concentrations in gestational tissues from women with term and preterm labor was undertaken to assess the extent of inflammatory activation associated with spontaneous labor and delivery. STUDY DESIGN: Extracts of amniotic, chorionic-decidual, and placental tissues from women delivered at term before labor (n = 15), at term after labor (n = 15), and preterm (n = 31) were assayed for interleukin 1beta, interleukin 6, and interleukin 8. RESULTS: In amniotic tissues of women delivered by spontaneous labor at term the median interleukin-6, interleukin-8, and interleukin-1beta concentrations were 3.8 to 5.4 times those of tissues from women delivered at term without labor (P <.05, Mann-Whitney U test). Interleukin-6 and interleukin-8 concentrations were also significantly increased (3. 3-4 times) in chorionic-decidual tissues. Marked increases (approximately 3-6 times) in the concentrations of all 3 cytokines were observed in both amniotic and chorionic-decidual tissues from women with preterm deliveries with respect to those from women with term deliveries after labor. Cytokine concentrations were significantly correlated within amniotic tissues from both women with term delivery after labor and women with preterm delivery and also in preterm chorionic-decidual tissues but not preterm placental tissues. Concentrations of cytokines in the tissues of women delivered preterm were not significantly affected by mode of delivery, treatment with antibiotics, or twin birth. In preterm tissues with evidence of intrauterine infection only amniotic interleukin-1beta concentrations were significantly elevated (P <. 05). Little or no labor-related change in cytokine concentrations was seen within placental tissues. CONCLUSIONS: Increased cytokine abundance in gestational membranes associated with labor supports the view that an inflammatory process is involved in both term and preterm labor. This process does not, however, appear to be evident in the villous placenta.     

Fragmented forms of insulin-like growth factor binding protein-1 in amniotic fluid of patients with preterm labor and intact membranes

To determine the clinical significance of an increase in various fragmented forms of insulin-like growth factor binding protein-1 (IGFBP-1) in amniotic fluid (AF), a retrospective cohort study was conducted in 103 consecutive patients with preterm labor and intact membranes. Amniotic fluid samples were cultured for aerobic and anaerobic bacteria, and mycoplasmas, and then assayed for matrix metalloproteinase-8. Fragmented-to-intact IGFBP-1 ratios were evaluated by densitometric analysis of Western blot assays. Intact IGFBP-1 (30 kDa) and 21, 17, and 12 kDa fragments were detected in AF. Median ratios of fragmented-to-intact IGFBP-1 were higher in patients whose neonates had significant morbidity than in those whose neonates did not (P < .05), in patients spontaneously delivered within 2 and 7 days from amniocentesis than in those delivered after 2 and 7 days (P < .05), and in patients with intra-amniotic infection/inflammation than in those without (P < .001). Collectively, fragmented IGFBP-1 in AF may be indicators for adverse perinatal outcomes.     

Maternal serum interleukin-6, interleukin-8, tumor necrosis factor-alpha and interferon-gamma in preterm labor

BACKGROUND: To find out whether preterm labor is associated with raised maternal serum concentrations of interleukin (IL)-6, IL-8, tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) and whether the measurement of these cytokines can be used to detect early intrauterine infection in preterm labor. METHODS: Cross-sectional study: 77 women in preterm labor, 47 controls of healthy preterm women not in labor and 19 women in term labor. The serum cytokines levels were measured by enzyme-linked immunosorbent assay (ELISA). The newborns of women who were in labor were followed up for evidence of infection. Differences between groups were tested using analysis of variance, Student's t-test and chi2-test. RESULTS: There was no significant difference in the concentration of all the cytokines measured between the different groups. No statistical difference was found in the concentration of the cytokines between women in preterm labor with ruptured membranes and those with intact membranes. There was also no difference found in the concentration of cytokines between women whose newborns had positive bacterial culture and those with negative culture. There was a positive correlation between the concentrations of IL-6, IL-8 and TNF-alpha. CONCLUSION: Serum levels of interleukin-6, interleukin-8 and tumor necrosis factor-alpha were not increased in preterm labor compared to normal control women. There is doubt regarding the usefulness of maternal serum measurement of these cytokines for the detection of early fetal infection in preterm labor, but this needs further evaluation.     

Vaginal indicators of amniotic fluid infection in preterm labor

OBJECTIVE: To determine whether vaginal interleukin-6, interleukin-8, neutrophils, bacterial vaginosis, and selected vaginal bacteria are predictors of amniotic fluid (AF) infection among women in preterm labor. METHODS: One hundred ninety-seven afebrile women in preterm labor with intact membranes had vaginal and AF samples collected for Gram stain, culture, and interleukin-8 and interleukin-6 determinations. Vaginal interleukin-6, interleukin-8, neutrophils, and vaginal flora were compared in women with positive and negative AF cultures. The negative AF culture group was subdivided according to AF interleukin-6 concentration. Logistic regression was used to examine the associations between vaginal cytokines and flora and AF infection or elevated AF interleukin-6. RESULTS: The vaginal interleukin-8 concentration and neutrophil count were significantly higher with both AF infection and elevated concentrations of AF interleukin-6 and interleukin-8. The vaginal interleukin-6 concentration was not associated with AF infection or high concentration of AF cytokines. Amniotic fluid infection was associated with bacterial vaginosis or intermediate vaginal flora by Gram stain, absence of hydrogen peroxide-producing Lactobacillus, and presence of vaginal Bacteroides ureolyticus and Fusobacterium. Vaginal interleukin-8 levels greater than 30 ng/mL had 80% sensitivity and a positive predictive value of 35%, and an abnormal vaginal Gram stain (more than five neutrophils per 400x field, bacterial vaginosis species, or intermediate flora) had 90% sensitivity and a positive predictive value of 27% to detect AF infection or elevated AF interleukin-6. CONCLUSION: A high vaginal interleukin-8 concentration, abnormal vaginal Gram stain, absent hydrogen peroxide-producing Lactobacillus, and anaerobic vaginal flora were strongly associated with AF infection among women in preterm labor.     

High interleukin-16 concentrations in the early second trimester amniotic fluid: an independent predictive marker for preterm birth

Objective: Infection is believed to be one of frequent and important causes of preterm labor. We attempted to evaluate whether the level of inflammatory markers, e.g. interleukin-16 (IL-16), interleukin-18 (IL-18), and ferritin, in amniotic fluid at early second trimester can predict preterm birth. Methods: Amniotic fluid (AF) samples were collected from 350 pregnant women who had trans-abdominal amniocentesis for genetic indications at 16 to 20 weeks of gestation. AF levels of IL-16, IL-18 and ferritin levels were measured by immunoassay and were correlated with pregnancy outcomes. Results: Among the 350 pregnant women, 58 (16.6%) had preterm birth (<37 weeks gestation). AF levels of IL-16, IL-18, and ferritin were significantly higher in pregnant women with subsequent preterm birth. Multivariate analyses showed that a quartile higher of AF IL-16 level was significantly associated with preterm birth (OR: 3.09, 95% CI 1.52–6.27, p = 0.002). A receiver operating characteristic analysis revealed that an IL-16 cutoff value of 105 pg/ml was a reliable predictor of preterm birth (sensitivity, 90.2%; specificity, 52.7%; negative predictive value, 84.3%). Conclusion: It is feasible to predict preterm birth by measuring the AF levels of IL-16 especially for the pregnant women requiring genetic amniocentesis during early second trimester.     

Second-trimester amniotic fluid interleukin-10 concentration predicts preterm delivery.

OBJECTIVE: Interleukin-6 (IL-6) is an inflammatory cytokine that has been shown to be elevated in the amniotic fluid of patients with preterm labor. On the other hand, interleukin-10 (IL-10) is an anti-inflammatory cytokine that has been shown to inhibit the synthesis of other cytokines. We hypothesized that amniotic fluid IL-10 in the early second trimester is low in patients who subsequently develop preterm labor, and because of its deficiency, excessive inflammatory responses associated with IL-6 elevation lead to preterm labor and delivery. STUDY DESIGN: Amniotic fluid IL-6 and IL-10 levels were measured in 96 women who underwent genetic amniocentesis between 15 and 23 weeks' gestation. Levels of IL-6 and IL-10 were measured by immunoassay and correlated with demographic and pregnancy outcome information. RESULTS: Fifteen patients delivered at or before 36 weeks and 81 patients delivered after 36 weeks. There was an inverse correlation between amniotic fluid IL-10 concentration and gestational age at delivery. Similarly, an inverse correlation also existed between amniotic fluid IL-6 concentration and gestational age at delivery. CONCLUSIONS: Both IL-10 and IL-6 levels in second-trimester amniotic fluid obtained at the time of genetic amniocentesis appeared to be higher in patients who subsequently developed preterm delivery. Therefore, low amniotic fluid IL-10 production during the second trimester does not seem to be an etiology for preterm labor.     

Infection and labor. VI. Prevalence, microbiology, and clinical significance of intraamniotic infection in twin gestations with preterm labor

The purpose of this study was to establish the prevalence, microbiology, and outcome of microbial invasion of the amniotic cavity in twin gestation presenting with preterm labor and intact membranes. Amniocenteses were performed on both sacs of 46 women with twin gestations, preterm labor, and intact membranes. Indigo carmine was injected to ensure sampling of both amniotic sacs. Amniotic fluid was cultured for aerobic and anaerobic bacteria, Mycoplasma hominis, and Ureaplasma urealyticum. A positive amniotic fluid culture of at least one sac was noted in 10.8% (5/46) of patients admitted in preterm labor and in 11.9% (5/42) of women delivered of preterm neonates. Of the five patients with microbial invasion of the amniotic cavity, three had microorganisms isolated from both sacs. The presenting sac was involved in all cases, supporting an ascending route for microbial invasion of the amniotic cavity in twin gestation. Polymicrobial infection was found in three of the eight amniotic sacs with positive cultures. In two cases different organisms were isolated from each sac. All patients with positive amniotic fluid cultures were delivered of preterm infants within 48 hours of amniocentesis. Patients with positive amniotic fluid cultures presented with preterm labor at an earlier gestational age and with more advanced cervical dilatation than did women with negative amniotic fluid cultures. Clinical evidence of chorioamnionitis subsequently developed in two of five women with positive amniotic fluid cultures. The interval between amniocentesis and delivery was shorter in women with positive amniotic fluid cultures than in women with negative amniotic fluid cultures (median: 3.5 vs 168 hours, p less than 0.0001). Infants born to women with microbial invasion of the amniotic cavity had a lower median birth weight and a higher incidence of respiratory distress syndrome than those born to women with negative amniotic fluid cultures (birth weight: 1085 vs 1975 gm, p = 0.024; respiratory distress syndrome: 37.5% vs 8.3%, p = 0.04).     

A rapid interleukin-6 bedside test for the identification of intra-amniotic inflammation in preterm labor with intact membranes

Objective: Preterm birth is associated with 5–18% of pregnancies and is the leading cause of neonatal morbidity and mortality. Amniotic fluid (AF) interleukin-6 (IL-6) is a key cytokine for the identification of intra-amniotic inflammation, and patients with an elevated AF IL-6 are at risk for impending preterm delivery. However, results of the conventional method of measurement (enzyme-linked immunosorbent assay; ELISA) are usually not available in time to inform care. The objective of this study was to determine whether a point of care (POC) test or lateral-flow-based immunoassay for measurement of AF IL-6 concentrations can identify patients with intra-amniotic inflammation and/or infection and those destined to deliver spontaneously before term among women with preterm labor and intact membranes.

Methods: One-hundred thirty-six women with singleton pregnancies who presented with symptoms of preterm labor and underwent amniocentesis were included in this study. Amniocentesis was performed at the time of diagnosis of preterm labor. AF Gram stain and AF white blood cell counts were determined. Microbial invasion of the amniotic cavity (MIAC) was defined according to the results of AF culture (aerobic and anaerobic as well as genital mycoplasmas). AF IL-6 concentrations were determined by both lateral flow-based immunoassay and ELISA. The primary outcome was intra-amniotic inflammation, defined as AF ELISA IL-6?≥?2600?pg/ml.

Results: (1) AF IL-6 concentrations determined by a POC test have high sensitivity (93%), specificity (91%) and a positive likelihood ratio of 10 for the identification of intra-amniotic inflammation by using a threshold of 745?pg/ml; (2) the POC test and ELISA for IL-6 perform similarly in the identification of MIAC, acute inflammatory lesions of placenta and patients at risk of impending spontaneous preterm delivery.

Conclusion: A POC AF IL-6 test can identify intra-amniotic inflammation in women who present with preterm labor and intact membranes and those who will subsequently deliver spontaneously before 34 weeks of gestation. Results can be available within 20?min – this has important clinical implications and opens avenues for early diagnosis as well as treatment of intra-amniotic inflammation/infection.     

Intrauterine infection and preterm delivery: evidence for activation of the fetal hypothalamic-pituitary-adrenal axis

OBJECTIVE: We studied pregnant women in preterm labor with and without intrauterine infection to determine whether fetal hypothalamic-pituitary-adrenal axis activation occurs in the setting of infection-induced preterm parturition.Study Design: Amniotic fluid collected by amniocentesis and maternal blood from patients in preterm labor with intact membranes at 24 to 34 weeks' gestation were analyzed by radioimmunoassay for the steroid hormones estrone, estradiol, progesterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and cortisol. Amniotic fluid was also obtained for microbial culture and for interleukin 6 measurements by enzyme immunoassay. RESULTS: Patients with intrauterine infection (n = 11) had significantly higher amniotic fluid concentrations of dehydroepiandrosterone (539 +/- 79 pg/mL) and of cortisol (5.28 +/- 1.0 microg/dL) than did patients with preterm labor and preterm delivery without infection (n = 11; 273 +/- 82 pg/mL and 1.61 +/- 1.05 microg/dL, respectively) or patients with preterm labor and subsequent term delivery (n = 11; 202 +/- 79 pg/mL and 1.82 +/- 1.0 microg/dL, respectively). Furthermore those patients who were delivered within 7 days after enrollment (who were also more likely to have intrauterine infection) had higher amniotic fluid concentrations than did those who were not delivered within 7 days of both estrone (586 +/- 101 pg/mL vs 314 +/- 98 pg/mL) and estradiol (238 +/- 44 pg/mL vs 91 +/- 43 pg/mL). CONCLUSION: Intrauterine infection was associated with increased fetal adrenal androgen and cortisol biosynthesis, and delivery within 7 days after the onset of preterm labor was associated with increased placental estrogen synthesis. These data are consistent with fetal hypothalamic-pituitary-adrenal axis activation in the setting of infection-associated preterm delivery.     

Second-trimester amniotic fluid interleukin-10 concentration predicts preterm delivery

Objective: Interleukin-6 (IL-6) is an inflammatory cytokine that has been shown to be elevated in the amniotic fluid of patients with preterm labor. On the other hand, interleukin-10 (IL-10) is an anti-inflammatory cytokine that has been shown to inhibit the synthesis of other cytokines. We hypothesized that amniotic fluid IL-10 in the early second trimester is low in patients who subsequently develop preterm labor, and because of its deficiency, excessive inflammatory responses associated with IL-6 elevation lead to preterm labor and delivery.

Study design: Amniotic fluid IL-6 and IL-10 levels were measured in 96 women who underwent genetic amniocentesis between 15 and 23 weeks' gestation. Levels of IL-6 and IL-10 were measured by immunoassay and correlated with demographic and pregnancy outcome information.

Results: Fifteen patients delivered at or before 36 weeks and 81 patients delivered after 36 weeks. There was an inverse correlation between amniotic fluid IL-10 concentration and gestational age at delivery. Similarly, an inverse correlation also existed between amniotic fluid IL-6 concentration and gestational age at delivery.

Conclusions: Both IL-10 and IL-6 levels in second-trimester amniotic fluid obtained at the time of genetic amniocentesis appeared to be higher in patients who subsequently developed preterm delivery. Therefore, low amniotic fluid IL-10 production during the second trimester does not seem to be an etiology for preterm labor.     

Amniotic fluid matrix metalloproteinase-9 levels in women with preterm labor and suspected intra-amniotic infection.

OBJECTIVE: To determine the accuracy of amniotic fluid (AF) matrix metalloproteinase-9 measurements for diagnosing intra-amniotic infection in women with preterm labor. METHODS: We performed amniocenteses in 44 women between 22 and 35 weeks' gestation who presented to our center with preterm labor and clinical suspicion of intra-amniotic infection. Each sample was analyzed by glucose measurement, Gram stain, and culture for aerobes, anaerobes, and mycoplasmas. We tested the AF for matrix metalloproteinase-9 using gelatin zymography and a commercial enzyme-linked immunosorbent assay (ELISA) system. We calculated accuracy and confidence intervals (CIs) for AF matrix metalloproteinase-9, glucose, and Gram stain for diagnosing intra-amniotic infection, using culture as the criterion standard. RESULTS: All patients who had matrix metalloproteinase-9 detectable by ELISA also demonstrated matrix metalloproteinase-9 by zymography. Six cases of intra-amniotic infection were confirmed by culture (prevalence 14%). The performance statistics of AF matrix metalloproteinase-9 for diagnosing intra-amniotic infection were: sensitivity 83% (95% CI 53, 99), specificity 95% (95% CI 88, 99), positive predictive value 71% (95% CI 37, 99), and negative predictive value 97% (95% CI 92, 99). Two women had false-positive results; one had gram-negative rods on the AF Gram stain and developed clinical signs and symptoms of chorioamnionitis several hours after amniocentesis and the other had a purulent vaginal discharge and an AF glucose level less than 15 mg/dL. Both delivered within 24 hours of amniocentesis. CONCLUSION: Measuring matrix metalloproteinase-9 in the AF appeared to be reliable for diagnosing intra-amniotic infection. An elevated matrix metalloproteinase-9 concentration in the AF at a preterm gestational age may portend imminent delivery regardless of microbiologic confirmation of intra-amniotic infection.     

Human beta-defensin-2: a natural antimicrobial peptide present in amniotic fluid participates in the host response to microbial invasion of the amniotic cavity.

OBJECTIVE: Human beta-defensin-2 (HBD-2) is a potent antimicrobial peptide that is part of the innate immune response. The purpose of this study was to determine whether HBD-2 is present in amniotic fluid and if its concentration changes with microbial invasion of the amniotic cavity (MIAC) and labor. STUDY DESIGN: Amniotic fluid was retrieved by amniocentesis from 318 patients in the following groups: (1) mid-trimester (n=75); (2) term not in labor (n=28) and in labor (n=51); (3) preterm labor and intact membranes without MIAC who delivered at term (n=36), who delivered preterm without MIAC (n=52), and preterm labor with MIAC who delivered preterm (n=25); and (4) preterm premature rupture of membranes (preterm PROM) with (n=25) and without MIAC (n=26). MIAC was defined as a positive amniotic fluid culture for microorganisms. Amniotic fluid HBD-2 concentrations were determined using a sensitive and specific ELISA. Non-parametric statistics were used for analysis. RESULTS: (1) HBD-2 was detected in all amniotic fluid samples; (2) the concentration of HBD-2 did not change with gestational age from mid-trimester to term (p=0.8); (3) intra-amniotic infection was associated with a significant increase in amniotic fluid concentrations of HBD-2 in both women with preterm labor and intact membranes, and women with preterm PROM (p<0.05 for each comparison); (4) patients with preterm labor and a negative amniotic fluid culture who delivered preterm had a higher median amniotic fluid HBD-2 concentration than those with preterm labor who delivered at term (p=0.001); and (5) among patients with preterm labor without MIAC, those who had intra-amniotic inflammation (amniotic fluid white blood cell count>100 cells per mL) had a higher median amniotic fluid concentration of HBD-2 than those without this condition (p<0.002). CONCLUSION: (1) Amniotic fluid contains HBD-2, a natural antimicrobial peptide, and this may account for some of the antimicrobial activity of amniotic fluid; (2) amniotic fluid HBD-2 concentrations are increased in women with MIAC, regardless of the membrane status (intact membranes or PROM); and (3) we propose that amniotic fluid HBD-2 is part of the innate immune system within the amniotic cavity.     

The association of occult amniotic fluid infection with gestational age and neonatal outcome among women in preterm labor.

To evaluate the relationships between gestational age, neonatal outcome, and amniotic fluid (AF) bacteria, we obtained AF from women with intact membranes in idiopathic preterm labor. Positive cultures were obtained from 20 (19%) of 105 women. The frequency of positive cultures was inversely related to gestational age: 23-26 weeks, nine of 20; 27-30 weeks, four of 24; and 31-34 weeks, seven of 61 (chi2 for trend, P less than .001). Fusobacterium nucleatum, Bacteroides ureolyticus, and Ureaplasma urealyticum were the most common isolates. Facultative and anaerobic bacteria were more commonly isolated from women at less than 30 weeks' gestation, and Ureaplasma urealyticum was commonly isolated at greater than 30 weeks' gestation. Forty percent of the patients identified as having positive AF facultative and anaerobic cultures by the research laboratory had negative cultures in the clinical laboratory. Clinical characteristics and maternal white blood cell count and differential did not differ between women with and without positive cultures. Elevated C-reactive protein levels and a positive AF Gram stain were the two most sensitive and specific methods to predict positive AF cultures. Women with positive cultures delivered a median of 1.0 day after enrollment, compared with 28.5 days for women with negative cultures. The median gestational age at delivery for women with positive cultures was 27.5 weeks, and the median birth weight was 866 g. Positive AF cultures were associated with respiratory distress syndrome, bronchopulmonary dysplasia, and neonatal death. If occult AF infection among women in preterm labor is a treatable cause of preterm birth, then treatment could markedly reduce both perinatal morbidity and mortality.     

Infection and labor. V. Prevalence, microbiology, and clinical significance of intraamniotic infection in women with preterm labor and intact membranes

Amniotic fluid was retrieved by amniocentesis from 264 patients with preterm labor and intact membranes admitted to Yale-New Haven Hospital from Jan. 1, 1985, to July 31, 1988. The prevalence of a positive amniotic fluid culture was 9.1% (24/264). A total of 111 patients (42%) delivered preterm neonates, and 24 (21.6%) of those had positive amniotic fluid cultures. The diagnostic indexes of the Gram stain of amniotic fluid in the prediction of a positive amniotic fluid culture were as follows: sensitivity, 79.1%; specificity, 99.6%; positive predictive value, 95%; and negative predictive value, 98%. Endotoxin was detected with the limulus amebocyte lysate assay in 4.9% (13/264) of patients with preterm labor. All patients with endotoxin in the amniotic fluid delivered preterm neonates. The three most frequently isolated organisms were Ureaplasma urealyticum (n = 6), Fusobacterium species (n = 5), and Mycoplasma hominis (n = 4). Clinical chorioamnionitis was present in only 12.5% of the patients with positive amniotic fluid cultures. Women with positive amniotic fluid cultures had lower gestational ages and more advanced cervical dilatation on admission than women with negative cultures. Preterm infants born to mothers with positive amniotic fluid cultures had a higher incidence of respiratory distress syndrome and infectious complications than preterm neonates born after negative amniotic fluid cultures. These data underscore the frequency and importance of intraamniotic infections in women with preterm labor.     

Amniotic fluid infection, cytokines, and adverse outcome among infants at 34 weeks' gestation or less.

OBJECTIVE: We examined the hypothesis that amniotic fluid (AF) infection and elevated cytokine concentrations may cause neonatal injury beyond that expected solely from prematurity. METHODS: The effects of exposure to AF infection and elevated cytokine concentrations were measured in 151 infants born to afebrile women in preterm labor with intact membranes at less than or equal to 34 weeks' gestation. Amniotic fluid was collected by amniocentesis for culture and determination of tumor necrosis factor-alpha and interleukin-6. Cytokine concentrations, stratified by AF infection, were compared for three gestational age groups. We then examined the associations between a positive AF culture or elevated AF tumor necrosis factor-alpha concentration and adverse neonatal outcomes, adjusted for birth weight. RESULTS: Amniotic fluid from 45 (30%) of 151 pregnancies had microorganisms, an elevated tumor necrosis factor-alpha concentration, or both. Amniotic fluid cytokine concentrations were significantly higher among women in preterm labor at less than or equal to 30 weeks, compared with 31-34 weeks. Nine of 11 infants who died at less than or equal to 24 hours of age had AF infection or elevated AF tumor necrosis factor-alpha. For the 140 surviving infants, AF infection and/or an elevated AF tumor necrosis factor-alpha was associated with respiratory distress syndrome (adjusted odds ratio [OR] 1.7), grade 3-4 intraventricular hemorrhage (adjusted OR 2.2), necrotizing enterocolitis (adjusted OR 1.8), and multiple organ dysfunction (adjusted OR 3.0). CONCLUSION: Among infants born at less than or equal to 34 weeks to women who have intact membranes and are initially afebrile, those exposed to AF bacteria or cytokines have more adverse neonatal outcomes than unexposed infants of similar birth weight.     

The incidence of positive amniotic fluid cultures in patients preterm labor with intact membranes

The possible relationship between intrauterine infection and preterm labor has received considerable attention in recent years. The purpose of this study was twofold: first, to determine the frequency of asymptomatic infection in patients who came to the hospital in preterm labor, and second, to determine the significance of a positive amniotic fluid culture in relation to latency period and likelihood of preterm delivery. Patients who came to the hospital in preterm labor with intact membranes between 20 and 35 weeks' gestation underwent transabdominal amniocentesis. Amniotic fluid was sent for Gram stain and culture. Patients received tocolytic therapy as clinically indicated. Of 127 patients cultured, seven (5.5%) had positive amniotic fluid cultures. These patients had a significantly decreased latency period from amniocentesis to delivery (4.4 days versus 28.6 days), and a significantly increased chance of being delivered of preterm infants (100% versus 52.5%), as compared with patients with negative cultures. The rate of positive Gram stain was 7 of 125 positive. However, there was no correlation between positive Gram stain and positive culture results. Similarly, positive Gram stain results were not associated with any difference in the latency period or rate of preterm delivery.     

Predictive value of intra-amniotic and serum markers for inflammatory lesions of preterm placenta

Objective

To compare the relative predictive values of amniotic fluid (AF) matrix metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), and serum C-reactive protein (CRP) for histologic chorioamnionitis and intra-amniotic infection in women with preterm labor or preterm premature rupture of membranes (PROM).

Study design

This retrospective cohort study included 99 consecutive women with preterm labor or preterm PROM (21–35 weeks’ gestation) who delivered within 72 h of transabdominal amniocentesis. The AF was cultured for aerobic and anaerobic bacteria and for genital mycoplasmas and was assayed for MMP-9 and IL-6 levels. Maternal serum CRP was measured immediately after amniocentesis. The placentas were examined histologically.

Main outcome measures

histologic chorioamnionitis and intra-amniotic infection.

Results

The prevalence of histologic chorioamnionitis and a positive AF culture was 44% (44/99) and 28% (28/99), respectively. In predicting intra-amniotic infection, AF MMP-9 had a significantly higher area under the curve (AUC: 0.94 [95% CI, 0.87–0.98]) than AF IL-6 (0.87 [95% CI, 0.78–0.84]; P < 0.05) and serum CRP (0.76 [95% CI, 0.66–0.84]; P < 0.001) and a higher sensitivity and specificity than serum CRP (P < 0.01, respectively). However, in predicting histologic chorioamnionitis, there were no significant differences in AUCs among the three tests (AF MMP-9: 0.78 [95% CI, 0.68–0.85]; AF IL-6: 0.76 [95% CI, 0.66–0.84]; serum CRP: 0.76 [95% CI, 0.66–0.84]). In a sub-analysis of 71 women without intra-amniotic infection, histologic chorioamnionitis was associated with an elevated serum CRP level (P < 0.05), but not with the level of AF IL-6 or MMP-9 (P = 0.232 and P = 0.402, respectively).

Conclusions

The AF MMP-9 has a better overall diagnostic performance than the AF IL-6 and maternal serum CRP in predicting intra-amniotic infection. However, the serum CRP level obtained up to 72 h before delivery appears to be an important marker for early identification of histologic chorioamnionitis in women without intra-amniotic infection.