Cytokines in normal and abnormal parturition: elevated amniotic fluid interleukin-6 levels in women with premature rupture of membranes associated with intrauterine infection

Signal for term parturition is of trophoblast and therefore of fetal origin

Up to now we know, that cytokines are key intermediates in the mechanisms, responsible for intrauterine activation in case of intra amniotic infection. The aim of our study was to investigate the role of cytokine- and prostaglandin production in normal term labor. Release of Il-6, Il-1 beta, TNF-alpha, PGE2, PGF2 alpha, was monitored in vaginal secretions originating from uterine cavity, cervix and vagina during normal course of labor. Cells from fetal membranes, decidua and villous trophoblast, obtained from placentas of patients after spontaneous delivery (n = 12), or without labor, after elective cesarean section (n = 12), were cultured, in order to identify cytokine and prostaglandin producing cells. In all cases, term labor and parturition was associated with strongly elevated cytokine- and prostaglandin concentrations in cervical secretions. Cell culture experiments clearly demonstrated, that cells from villous trophoblast, cultured after spontaneous delivery produced significantly more cytokines and prostaglandins than cells form villous trophoblast, cultured after elective cesarean section. Cells from fetal membranes also produced more Il-6 and PGE2 after labor. In contrast to that, cells from decidua produced similar amounts of cytokines and prostaglandins before and after spontaneous term labor. Therefore we conclude, that the signal for term labor and delivery is of trophoblast and so of fetal origin.

Soluble tumor necrosis factor receptors and soluble interleukin-6 receptor in fetal and maternal sera, coelomic and amniotic fluids in normal and pre-eclamptic pregnancies

The aim of this study was (a) to measure soluble tumor necrosis factor receptors (sTNF-Rs) and soluble interleukin-6 receptor (sIL-6-R) in coelomic and amniotic fluids, cord and maternal sera in pregnancy and labor, (b) to examine whether the changes in concentrations of biologically active TNF and IL-6 are related to changes in their soluble receptors, and (c) to determine if levels of soluble receptors in pre-eclamptic disorders differ from normal pregnancies at delivery. Materials collected from 206 women during pregnancy and at delivery were analyzed for soluble receptors by enzyme-linked immunosorbent assay (ELISA). All receptors were present in higher concentrations in coelomic than in the corresponding amniotic fluid. Concentrations increased in amniotic fluid from first to second trimester. The level of sIL-6-R then remained unchanged to term, but there was a decrease in the sTNF-Rs which might account for the simultaneous appearance of bioactive TNF. Labor did not affect the concentration of any receptor in amniotic fluid. In maternal serum, sTNF-Rs increased with gestational age and labor in parallel with IL-6. The origin and physiological importance of these soluble receptors are still unknown. In pre-eclamptic disorders p55 sTNF-R was elevated in maternal serum before initiation of labor compared to normal pregnancy.

Amniotic fluid interleukin-6: a sensitive test for antenatal diagnosis of acute inflammatory lesions of preterm placenta and prediction of perinatal morbidity

OBJECTIVE

Our purpose was to determine whether amniotic fluid concentrations of interleukin-6 are of value in the antenatal diagnosis of acute inflammatory lesions (histologic chorioamnionitis) of preterm placenta and in the prediction of perinatal morbidity and mortality.

STUDY DESIGN

The relation among placental histologic findings, perinatal outcome, and amniotic fluid interleukin-6 concentrations was examined in 50 consecutive patients who delivered preterm neonates within 72 hours after amniocentesis. Interleukin-6 was determined by enzyme-linked immunosorbent assays. Receiver-operator characteristic curve was used for analysis.

RESULTS

Patients with acute histologic chorioamnionitis had significantly higher median amniotic fluid interleukin-6 concentrations than patients without histologic chorioamnionitis (median 70.8 ng/ml, range 0.7 to 499.2 ng/ml vs median 2.9 ng/ml, range 0.8 to 16.0 ng/ml, respectively; p < 0.00001). An amniotic fluid interleukin-6 concentration > 17 ng/ml had a sensitivity of 79% (23/29) and a specificity of 100% (21/21) in the diagnosis of acute histologic chorioamnionitis and a sensitivity of 69% (18/26) and a specificity of 79% (19/24) in the prediction of significant neonatal morbidity (defined as neonatal sepsis, respiratory distress syndrome, pneumonia, intraventricular hemorrhage, bronchopulmonary dysplasia, or necrotizing enterocolitis) and mortality. These sensitivities were significantly higher than those of amniotic fluid culture (79% vs 38%, p < 0.005; 69% vs 27%, p < 0.01, respectively).

CONCLUSIONS

Amniotic fluid interleukin-6 is a sensitive test for the prospective diagnosis of acute histologic chorioamnionitis and the identification of neonates at risk for significant morbidity and mortality.

Maternal plasma and placental immunoreactive corticotrophin-releasing factor concentrations in infection-associated term and pre-term delivery

The present study aimed to investigate whether microbial invasion of the amniotic cavity affects maternal plasma or placental immunoreactive corticotrophin releasing factor (ir-CRF) concentrations in pregnant women with pre-term or term labour. A cross-sectional study was conducted collecting blood samples in: (1) women with pre-term labour and intact membranes (25-36 weeks), with or without microbial invasion of the amniotic cavity (subdivided into three groups: 1A, no microbial invasion of the amniotic cavity, delivery at term, n = 54; group 1B, delivery < 48 h, no microbial invasion of the amniotic cavity, n = 10; group 1C, delivery < 48 h, microbial invasion of the amniotic cavity, n = 8); (2) women at term, not in labour and without microbial invasion of the amniotic cavity (n = 15); (3) women in spontaneous active labour at term without (A) (n = 55) or with (B) (n = 16) microbial invasion of the amniotic cavity; and (4) healthy women not in labour at 25-36 weeks of gestation (n = 25). Specimens of trophoblast tissue were collected from pregnant women with pre-term labour (no microbial invasion of the amniotic cavity, n = 6; microbial invasion of the amniotic cavity, n = 4) or delivering at term (no microbial invasion of the amniotic cavity, n = 8; microbial invasion of the amniotic cavity, n = 4). A specific radioimmunoassay on acidic extracts of plasma or placental specimens was used.(ABSTRACT TRUNCATED AT 250 WORDS)

The value of amniotic fluid interleukin-6, white blood cell count, and gram stain in the diagnosis of microbial invasion of the amniotic cavity in patients at term

PROBLEM

Subclinical microbial invasion of the amniotic cavity occurs in 18.8% of women with term labor and intact membranes and in 34% of patients with term PROM and is a risk factor for the development of puerperal infection related morbidity. Although amniotic fluid white blood cell count, interleukin-6 determination, and Gram stain examination have been used for the diagnosis of intrauterine infection in patients with preterm labor and preterm premature rupture of membranes, no information is available about the accuracy and specific cut-off values for these tests in patients at term. The purpose of this study was to compare the performance of the amniotic fluid Gram stain examination, white blood cell count, and interleukin-6 determination in the identification of microbial invasion of the amniotic cavity in patients at term with and without PROM.

METHOD

Amniotic fluid was retrieved from 148 patients with term gestations (90 patients with spontaneous labor and intact membranes and 58 patients with PROM). Samples were cultured for bacteria and Mycoplasma species. Amniotic fluid Gram stain, white blood cell count, and interleukin-6 determinations (ELISA, sensitivity: 43 pg/ml) were performed in all samples. Microbial invasion of the amniotic cavity was defined as a positive amniotic fluid culture for microorganisms. Analysis was conducted using Mann-Whitney U test, Fisher's exact test, receiver operating characteristic curves and logistic regression.

RESULTS

Patients with spontaneous labor and intact membranes: The prevalence of microbial invasion of amniotic cavity in this group was 15.6% (14/90). The most sensitive test for the detection of microbial invasion of the amniotic cavity was amniotic fluid interleukin-6 determination (sensitivity for: interleukin-6 > or = 5.7 ng/ml = 86%, white blood cell count > or = 20 cells/mm3 = 64%, Gram stain = 28%). The most specific test was the Gram stain of the amniotic fluid (specificity for: Gram stain = 84%, interleukin-6 = 79% and white blood cell count = 63%). Multiple logistic regression demonstrated that amniotic fluid interleukin-6 concentration was the only covariate that retained statistical significance when intrauterine infection was used as outcome variable. Patients with PROM: The prevalence of a positive amniotic fluid culture in this group was 39.7% (23/58). Logistic regression demonstrated that only interleukin-6 retained a significant relationship with the results of amniotic culture when all variables were entered simultaneously into a model to predict amniotic fluid culture results. The most sensitive tests for the detection of intrauterine infection were interleukin-6 determination and white blood cell count (sensitivity for interleukin-6 > or = 3.4 ng/ml and white blood cell count > or = 20 cells/mm3 = 69.6% for both). The most specific test was Gram stain (97.1%).

CONCLUSIONS

Amniotic fluid interleukin-6 determination is the best rapid test for the detection of microbial invasion of the amniotic cavity in patients at term with and without PROM. When this test is not available, amniotic fluid Gram stain and white blood cell count represent valid diagnostic tools to assess the microbial state of amniotic cavity.

Cytokine levels in amniotic fluid and inflammatory changes in the placenta from normal deliveries at term

Cytokine levels in amniotic fluid have been shown to increase towards term in normal pregnancies, and may play a regulatory role in parturition by stimulating the local production of prostaglandins. The work reported in the present paper was conducted in order to test the hypothesis that the increased cytokine levels may be induced by a subclinical inflammatory reaction in intrauterine tissues. The concentrations of tumor necrosis factor (TNF), interleukin 1 (IL-1), interleukin 2 (IL-2) and interleukin 6 (IL-6) were determined in samples of amniotic fluid from 38 women in delivery at term, after a clinically normal pregnancy. In 33 of the cases, tissue material was available for histological examination. In these, the extent of inflammatory cell infiltration was assessed in the fetal membranes, placenta and umbilical cord. A close interrelation was observed between the levels of the mediators typically released during inflammatory processes (TNF, IL-1, IL-6). Frank chorioamnionitis was not found in any of the histological specimens, although most placentae showed varying degrees of granulocyte infiltration in the fibrin layer under the chorion, sometimes also in the chorionic membrane. The degree of such leukocytic infiltration correlated positively with the levels of TNF, IL-1 and IL-6. These findings lend support to the hypothesis that a low-level inflammatory process may be a normal occurrence in the term placenta, and that this process may induce the production of cytokines, which, in turn, may play a role in the regulation of parturition. Such inflammation could be due to exposure of the fetal membranes to microbial material from the vagina, as the cervix dilates towards term.

Augmentation of fetal granulopoiesis with chorioamnionitis during the second trimester of gestation

Chorioamnionitis is a major hazard to pregnancy in the second trimester. It affects the fetomaternal unit, causing febrile illness in the mother. The fetus eventually is expelled because uterine contractions can no longer be suppressed after a certain stage of the disease. To determine the effects of chorioamnionitis on the fetus we examined fetal hematopoiesis, which is, for the most part, located extramedullarily during the second trimester of gestation. The study was performed morphometrically on sections of fetal tissues; the results are given as an increase of cells per square millimeter. In chorioamnionitis the fetuses (n = 18) showed increased granulopoiesis in the parenchyma of the liver (x12), in the spleen (x 5), in the portal triads of the liver (x3), and in the bone marrow (x1.35). Erythropoiesis and total hematopoiesis were reduced in all compartments. Inflammatory disease in the mother other than chorioamnionitis did not alter fetal hematopoiesis (n = 13). Under normal conditions fetal liver granulopoiesis is at a very low level within the sinusoids, but an early and substantial increase can be seen most easily in this location during infection; chorioamnionitis can thus be diagnosed from the fetal liver alone. Alterations in fetal hematopoiesis might be caused by cytokines generated at the fetomaternal interface during chorioamnionitis.

Bacterial vaginosis and vaginal microorganisms in idiopathic premature labor and association with pregnancy outcome

The vaginal microflora of 49 women in idiopathic preterm labor was compared with that of 38 term controls to determine whether the presence of bacterial vaginosis (BV) and/or specific microorganisms would influence the rate of preterm delivery. Demographic factors, pregnancy outcome, and reproductive history were also studied. BV, as defined by the presence of clue cells in a vaginal wet mount and characteristic microbial findings in a stained vaginal smear and vaginal culture, was more common in women with preterm labor and delivery than in controls (P < 0.01). The condition, diagnosed in 41% of women who had both preterm labor and delivery (n = 22) and in 11% each of women who had preterm labor but term delivery (n = 27) and controls, was associated with a 2.1-fold risk (95% confidence intervals, 1.2 to 3.7) for preterm birth prior to 37 weeks of gestation. BV was associated with low birth weight. Of 49 women with preterm labor, 67% (8 of 12) of women with BV were delivered of low-birth-weight neonates (< 2,500 g) compared with 22% (8 of 37) of women without the condition (P < 0.0005). The presence of hydrogen peroxide-producing facultative Lactobacillus spp. was strongly negatively associated with both preterm delivery and BV. BV-associated microorganisms, i.e., Mobiluncus, Prevotella, and Peptostreptococcus species, Porphyromonas asaccharolytica, Fusobacterium nucleatum, Mycoplasma hominis, and high numbers of Gardnerella vaginalis were significantly associated with preterm delivery; all species also strongly associated with BV (P = 0.0001 for each comparison). Mobiluncus curtisii and Fusobacterium nucleatum were recovered exclusively from women with preterm delivery. Our study clearly indicates that BV and its associated organisms are correlated with idiopathic premature delivery.

Interleukin-6 levels in amniotic fluid in normal and abnormal pregnancies: preeclampsia, small-for-gestational-age fetus, and premature labor

OBJECTIVE

Our purpose was to determine if abnormal amniotic fluid interleukin-6 levels correlate with pregnancies complicated by preeclampsia, small-for-gestational-age fetus, and premature labor.

STUDY DESIGN

A case control study design was used to compare third-trimester amniotic fluid interleukin-6 levels from women with normal pregnancies (n = 25) and pregnancies complicated by preeclampsia (n = 15), small-for-gestational-age perinates (n = 8), and premature labor (n = 29).

RESULTS

Amniotic fluid interleukin-6 levels in women with preeclampsia and small-for-gestational-age perinates were less than in controls (p < 0.01). Interleukin-6 levels in women with preterm labor refractory to tocolysis were higher than those in women with preterm labor responsive to tocolysis (p < 0.01).

CONCLUSIONS

Interleukin-6 is normally present in amniotic fluid. In the third trimester of pregnancy low levels correlate with small-for-gestational-age fetuses and preeclampsia, whereas elevated levels correlate with preterm labor and delivery.

A comparative study of the diagnostic performance of amniotic fluid glucose, white blood cell count, interleukin-6, and gram stain in the detection of microbial invasion in patients with preterm premature rupture of membranes

OBJECTIVE

Our aim was to compare the value of amniotic fluid tests for the detection of microbial invasion of the amniotic cavity and in the prediction of the amniocentesis-to-delivery interval and neonatal complications in patients with preterm premature rupture of membranes.

STUDY DESIGN

Amniotic fluid was obtained by transabdominal amniocentesis from 110 consecutive patients with preterm premature rupture of membranes. Fluid was cultured for aerobic and anaerobic bacteria, as well as mycoplasmas. Amniotic fluid analysis included a Gram stain examination, white blood cell count, and glucose and interleukin-6 determinations. Logistic regression and survival techniques (proportional hazards model) were used for statistical analysis.

RESULTS

(1) The prevalence of positive amniotic fluid cultures in patients with preterm premature rupture of membranes was 38% (42/110); (2) patients with microbial invasion had a shorter amniocentesis-to-delivery interval and a higher neonatal complication rate than patients with negative cultures; (3) the most sensitive test for the detection of microbial invasion of the amniotic cavity was amniotic fluid interleukin-6 determinations (cutoff 7.9 ng/ml) (sensitivity: for IL-6 80.9%; for white blood cell count 57.1%; for glucose 57.1%; for Gram stain 23.8%; p < 0.05 for all comparisons); (4) the most specific test for the detection of microbial invasion was the Gram stain of amniotic fluid (specificity: for Gram stain 98.5%; for white blood cell count 77.9%; for interleukin-6 75%; for glucose 73.5%; p < 0.01 for all); (5) of all amniotic fluid tests, interleukin-6 determination was the only test that had significant clinical value in the prediction of the amniocentesis-to-delivery interval and neonatal complications.

CONCLUSION

Interleukin-6 concentrations in amniotic fluid are a better predictor of microbial invasion of the amniotic cavity, amniocentesis-to-delivery interval and neonatal complications than the amniotic fluid Gram stain, glucose, or white blood cell count in patients with preterm premature rupture of membranes.

Amniotic fluid interleukin-6 determinations are of diagnostic and prognostic value in preterm labor

PROBLEM

The purpose of this study was to determine if amniotic fluid concentrations of the interleukin-6 (IL-6) are of value in diagnosis of microbial invasion of the amniotic cavity and in the prediction of failure of tocolysis, preterm delivery and perinatal morbidity and mortality.

METHOD

Amniotic fluid was obtained by transabdominal amniocentesis from 146 consecutive patients admitted with the diagnosis of preterm labor and intact membranes. Fluid was cultured for aerobic and anaerobic bacteria as well as for mycoplasmas. Amniotic fluid IL-6 levels were measured using a monoclonal antibody-based enzyme-linked immunosorbent assay with a sensitivity of 0.03 ng/ml. Logistic regression and Cox's proportional hazards model were used to examine the effect of several variables on dichotomous outcomes or interval to delivery.

RESULTS

Patients with a positive amniotic fluid culture had a significantly higher amniotic fluid IL-6 concentrations than patients with a negative culture (median 91.2 ng/ml, range 0.9 to 437 ng/ml versus median 0.4 ng/ml, range < 0.3 to 195 ng/ml, respectively; P < .0001). An amniotic fluid IL-6 concentration of greater than or equal to 11.3 ng/ml had a sensitivity of 93.3% (14 of 15) and a specificity of 91.6% (120 of 131). All patients with an amniotic fluid IL-6 concentration above 11.3 ng/ml and a negative amniotic fluid culture (N = 11) delivered preterm and all placenta available for examination (N = 7) had histologic evidence of chorioamnionitis. Amniotic fluid concentrations of IL-6 were an independent predictor of preterm delivery, amniocentesis-to-delivery interval and neonatal morbidity and mortality. Moreover, IL-6 concentrations added significant information to the prediction of these outcomes to that provided only by clinical information such as cervical dilatation, gestational age at admission or at delivery.

CONCLUSION

IL-6 is a sensitive and rapid test for the detection of microbial invasion of the amniotic cavity and for identifying women at risk for spontaneous preterm delivery and neonates at risk for morbidity and mortality.

Tumor necrosis factor, interleukin-1, and interleukin-6 in normal human pregnancy

OBJECTIVE

Our purpose was to investigate the cytokines, tumor necrosis factor, interleukin-1, and interleukin-6 in normal human pregnancy and labor.

STUDY DESIGN

Bioassays were used to measure these factors in extraembryonic coelomic fluid, amniotic fluid, placenta, and maternal and cord serum.

RESULTS

Little or no tumor necrosis factor, interleukin-1, or interleukin-6 was found in coelomic fluid or amniotic fluid in the first trimester. Interleukin-6 appeared in second-trimester amniotic fluid. At term tumor necrosis factor was present (median 17 pg/ml) and increased with the onset of labor (median 58 pg/ml), as did interleukin-1 (median 188 to 680 pg/ml) and interleukin-6 (median 399 to 4800 pg/ml). Maternal serum interleukin-6 increased during pregnancy with a further increment with the onset of labor. Cord interleukin-6 also increased with labor but at a lower level.

CONCLUSION

The cytokines tumor necrosis factor, interleukin-1, and interleukin-6 may play a role in the onset of normal labor.

Association between pulmonary and gastric inflammatory cells on the first day of life in preterm infants

It has been shown that inflammatory cells in the newborn lung are fetal in origin, whereas those in the amniotic fluid are maternal. In order to explore the relationship between fetal amnionitis and neonatal pneumonitis, we collected paired samples of gastric aspirate within 2 hours of birth, and bronchoalveolar lavage fluid within 24 hours of birth from intubated preterm infants. Leukocyte counts in bronchoalveolar lavage fluid correlated with the duration of membrane rupture (r = 0.68, P = 0.0001). There was a high degree of correlation between leukocyte counts in the two fluids (r = 0.86, P = 0.0001). The factors responsible for this association are unknown.

The role of prostaglandins in obstetrical disorders

All pregnancy-associated tissues are capable of producing prostaglandins including PGI2 and TXA2. In normal pregnancy there is a dominance of PGI2 over TXA2 which may contribute to the maternal circulatory adaptation to pregnancy. Furthermore, both fetoplacental PGI2 and TXA2 production are important regulators of the fetal blood supply. It has been clearly established that in pre-eclampsia PGI2 production decreases in the fetoplacental tissues and quite probably also in the maternal tissues. The effect of this change may be further exaggerated by the simultaneous stimulation in pre-eclampsia of TXA2 production. The reason for PGI2 deficiency is not known. Other vasoactive agents, such as endothelin, may act in concert with prostaglandins. Relative PGI2 deficiency is likely to exist also in IUGR and lupus anticoagulant syndrome of pregnancy. In the latter, lupus anticoagulant may directly inhibit the synthesis of PGI2. One study suggests PGI2 deficiency also in early pregnancies of women with a history of repeated abortions. Prostaglandin production increases during full-term labour, and similar but smaller changes also occur in preterm labour. A silent bacterial infection may trigger the onset of preterm labour through cytokine-stimulated increase of prostaglandin production. No data were found on prostaglandin production in post-term pregnancies. That oligo-polyhydramnios is possibly prostaglandin mediated is suggested by the control of polyhydramnios by indomethacin treatment. Smoking decreases the production of PGI2 and possibly increases that of TXA2, which may lead to decreased blood flow and IUGR. Which constituent of cigarette smoke exerts this effect is not known. Ethanol consumption causes aberrations in prostaglandin metabolism which cannot be directly connected with fetal alcohol effects.

Acute intrauterine hypoxia increases amniotic fluid prostaglandin F metabolites in the pregnant sheep

OBJECTIVE

Amniotic fluid infection promotes cytokine release, prostaglandin production, and premature labor. In several tissues local hypoxia also activates the secretion of cytokines. Many patients initially seen in premature labor carry small-for-gestational-age fetuses, a condition associated with intrauterine hypoxia. The purpose of our study was to determine whether a reduction in placental blood flow and subsequent acute hypoxia affects prostaglandin secretion by the placenta.

STUDY DESIGN

We chronically catheterized six pregnant sheep at 120 days of gestation. We placed catheters in the maternal and fetal femoral arteries and in the amniotic fluid cavity. A flow probe and snare were placed around the common uterine artery.

RESULTS

A 30-minute uterine circulation occlusion of 30% of its control value produced an increase in prostaglandin F metabolite from 790 +/- 157 to 944 +/- 184 pg/ml within 10 minutes (p < 0.01). Additional uterine blood flow reduction to 60% of control increased the amniotic fluid prostaglandin F metabolites concentration to 894 +/- 202 (p < 0.05, analysis of variance). No increase in mean intrauterine pressure was detected (p > 0.1).

CONCLUSIONS

We speculate that the prostaglandin increase in amniotic fluid in response to intrauterine hypoxia could eventually lead to premature labor. Whether the increase in prostaglandins is mediated by changes in cytokines is unknown at the present time.

Tumor necrosis factor-alpha selectively stimulates prostaglandin F2 alpha production by macrophages in human term decidua

OBJECTIVE

Our objective was to investigate the effect of tumor necrosis factor-alpha on prostaglandin production by human term decidual cell subtypes in vitro.

STUDY DESIGN

We measured the effect of tumor necrosis factor-alpha on prostaglandins F2 alpha, E2, D2, F metabolite, and E metabolite production by decidual cells (n = 4) with radioimmunoassay. We used flow cytometry after labeling with an antibody to histocompatibility antigen DR, L243, which is specific for macrophages in this tissue, to prepare pure populations of decidual macrophages (n = 3). Differences in prostaglandin output were analyzed by Wilcoxon and Kruskal-Wallis tests.

RESULTS

Tumor necrosis factor-alpha stimulated prostaglandin F2 alpha output by unfractionated decidual cells, without altering the output of any other prostaglandins. Tumor necrosis factor-alpha (10 nmol/L) increased prostaglandin F2 alpha production from decidual macrophages (HLA-DR-positive cells) by about threefold: from a median of 727 (range 423 to 1226) to a median of 1974 (range of 1550 to 2201), fmol/10(6) cells per 18 hours, as compared with a 1.4-fold increase from nonmacrophages from a median of 247 fmol/10(6) cells per 18 hours (range 125 to 611) to a median of 340 fmol/10(6) cells per 18 hours (range 201 to 505).

CONCLUSION

Stimulation of decidual prostaglandin F2 alpha production by tumor necrosis factor-alpha may be important in the etiology of spontaneous labor at term or preterm labor associated with infection.

Tumor necrosis factor in preterm and term labor

OBJECTIVE

Our objective was to determine if labor (term and preterm) and microbial invasion of the amniotic cavity were associated with changes in amniotic fluid concentrations of tumor necrosis factor.

STUDY DESIGN

Amniotic fluid was retrieved by transabdominal amniocentesis from 269 women in the following groups: midtrimester (n = 38), preterm labor with intact membranes (n = 52), preterm premature rupture of membranes (n = 74), term in active labor (n = 84), and term not in labor (n = 21). Fluid was cultured for aerobic and anaerobic bacteria and for Mycoplasma species. Tumor necrosis factor was measured with a commercially available enzyme-linked immunosorbent assay validated for amniotic fluid (sensitivity 60 pg/ml).

RESULTS

Amniotic fluid from pregnant women in the second and third trimesters who were not in labor did not contain tumor necrosis factor. Among women in preterm labor, 92.3% (12/13) of patients with a positive amniotic fluid culture had detectable tumor necrosis factor in the amniotic fluid (median 820 pg/ml, range less than 60 to 2340 pg/ml). In contrast, only 10.2% (4/39) of women with a negative amniotic fluid culture had detectable tumor necrosis factor. Histopathologic chorioamnionitis was found in all patients who had a positive amniotic fluid culture, and tumor necrosis factor was detectable in the amniotic fluid of all but one of these patients. Among women in active labor at term, 25% (21/84) had detectable tumor necrosis factor in the amniotic fluid. Tumor necrosis factor was detected more frequently in the amniotic fluid of patients with a positive amniotic fluid culture than in patients with a negative culture (46.6% [7/15] vs 20.2% [14/69], p = 0.047). Amniotic fluid concentrations of tumor necrosis factor were significantly higher in patients with preterm premature rupture of membranes, labor, and a positive amniotic fluid culture than in the other subgroups of patients with preterm premature rupture of membranes.

CONCLUSION

Parturition in the setting of microbial invasion of the amniotic cavity is associated with activation of the cytokine network as demonstrated by the detection of tumor necrosis factor in human amniotic fluid.

Interleukin-1 alpha and interleukin-1 beta in preterm and term human parturition

Interleukin-1 (IL-1) has been implicated in the mechanism of human parturition in the setting of infection. The purpose of this study was to determine the effect of labor (term and preterm) and microbial invasion of the amniotic cavity on amniotic fluid (AF) concentrations IL-1 alpha and IL-1 beta. AF was retrieved by transabdominal amniocentesis from the following groups of women: midtrimester genetic amniocentesis (16 to 18 wk) (N = 15), preterm labor with intact membranes (21 to 36 wk) with or without infection (N = 72), preterm premature rupture of membranes (PROM) (N = 88), and term not in labor or in active labor with or without infection (N = 58). AF was cultured for aerobic and anaerobic bacteria as well as Mycoplasmas. IL-1 was measured with a commercially available immunoassay validated for AF (sensitivity: IL-1 alpha, 157 pg/ml; IL-1 beta, 50 pg/ml). All women at midtrimester had undetectable AF IL-1 alpha and IL-1 beta. Among women in preterm labor with positive AF cultures, IL-1 alpha and IL-1 beta were detectable in the AF in 86.6% (13/15) and 100% (15/15), respectively. In contrast, all women with negative AF cultures without labor (N = 36) had undetectable AF IL-1 alpha concentrations and 52.7% (19/36) had undetectable AF IL-1 beta concentrations. Histopathological chorioamnionitis was present in 92.8% (13/14) of patients who had positive AF cultures and detectable IL-1 in the AF. IL-1 was significantly higher in patients with preterm PROM, labor, and positive AF cultures than in the other subgroups of patients with preterm PROM.(ABSTRACT TRUNCATED AT 250 WORDS)