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The origin and fate of hyaluronan in amniotic fluid.

The mechanisms which regulate the steady-state concentration and molecular weight of hyaluronan in the amniotic fluid of sheep at different gestational ages have been investigated. An attempt to trace the origin of the polysaccharide has been made by analyses of various fetal fluids (amniotic fluid, allantoic fluid, tracheal fluid, urine, and serum). The fate has been studied by injection of radioactively labelled hyaluronan into the amniotic cavity and following the tracer in fetal tissues and fluids. The concentration of hyaluronan in amniotic fluid varies considerably but is in the order of 5 mg/l at mid-pregnancy and decreases to 1 mg/l in late pregnancy. The polysaccharide has a Mr-distribution with a weight-average in the order of 10(6) at 10 to 13 weeks of gestation which decreases to 10(5) closer to term. Calculations show that urine contributes 0.1 and 0.5 mg of low-molecular (Mr = 10(4) hyaluronan per day in mid- and late pregnancy, respectively, and the lung 10-20% of that amount in the form of high-molecular weight polymer (Mr greater than 10(6). The hyaluronan disappears from the amniotic cavity by bulk flow due to fetal swallowing. It is taken up and degraded in the fetal intestine. Molecules of Mr = 10(3) can pass the intestinal barrier. Calculations show that about 0.5 mg and 1.0 mg of hyaluronan is eliminated per day from the amniotic fluid at 12 and 17 weeks of gestation, respectively. Thus, the higher rate of elimination and the relatively high urinary contribution in more mature fetuses explain the low concentration and Mr of amniotic hyaluronan in late gestation, whereas a slower elimination combined with a relatively larger contribution of high molecular weight hyaluronan both from lung and urine and possibly from other sources are responsible for the higher concentration and Mr of the compound in early pregnancy.

Allantois↗

IL-8 concentrations in maternal serum, amniotic fluid and cord blood in relation to different pathogens within the amniotic cavity.

OBJECTIVE: The association between elevated interleukin (IL)-8 concentrations in amniotic fluid and preterm delivery is well described. Little consideration has been given to the impact of different groups of microorganisms within the amniotic cavity on IL-8 concentration. METHODS: We collected amniotic fluid, placental tissue and amniotic membranes during preterm cesarean sections for bacterial culture. In addition, we determined IL-8 concentrations in maternal serum, amniotic fluid and cord blood and correlated them with the various intra-amniotic pathogens isolated by bacterial culture. RESULTS: IL-8 concentrations were determined in amniotic fluid in 107 cases, in cord blood in 185 cases and in maternal blood in 158 cases. Women with intra-amniotic Ureaplasma urealyticum infection had significantly higher amniotic fluid concentrations of IL-8 than those without (P< 0.001). In cord blood, we found significantly elevated IL-8 concentrations due to intra-amniotic infection with U. urealyticum (P=0.045) and other pathogens (P=0.04). In maternal sera, we found no significant elevation of maternal IL-8 in any of the groups. CONCLUSION: Intrauterine infection with U. urealyticum seems to play a profound role in the cascade of inflammation and increases IL-8 concentrations in amniotic fluid and cord blood.

Adult↗

Elevated amniotic fluid levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 in intra-amniotic infection.

OBJECTIVE: The study's objective was to determine and correlate amniotic fluid levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 in patients with and without intra-amniotic infection. STUDY DESIGN: Amniocentesis was performed on 41 pregnant women with preterm contractions, labor, or premature rupture of membranes. Intra-amniotic infection was defined as the presence of a positive amniotic fluid culture result. Amniotic fluid tests for Gram stain, glucose, leukocyte counts, creatinine level, pH, and specific gravity were performed. Amniotic fluid levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 were measured by an enzyme-linked immunoassay. Unlike in previous reports, cytokines were normalized by amniotic fluid creatinine levels. RESULTS: Fifteen patients had intra-amniotic infection and 26 did not. Amniotic fluid median levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 were significantly higher in pregnant women with intra-amniotic infection than in those without intra-amniotic infection (leukemia inhibitory factor median 3912 pg/mg creatinine, range 0.0-199314, vs 56 pg/mg creatinine, range 0. 0-12148, P =.01; interleukin 6 median 2005 ng/mg creatinine, range 27-4071, vs 990 ng/mg creatinine, range 7.5-3409, P =.005; interleukin 8: median 4933 ng/mg creatinine, range 0.0-55058, vs 61 ng/mg creatinine, range 0.0-2399, P =.005). Amniotic fluid levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 were positively correlated. CONCLUSIONS: The data indicate that leukemia inhibitory factor plays an important role in the pathogenesis of intra-amniotic infection. In addition, significant elevations of and correlations among amniotic fluid levels of leukemia inhibitory factor, interleukin 6, and interleukin 8 suggest that measurements of these cytokines in amniotic fluid may be of diagnostic and prognostic importance.

Adolescent↗

Antimicrobial peptides in amniotic fluid: defensins, calprotectin and bacterial/permeability-increasing protein in patients with microbial invasion of the amniotic cavity, intra-amniotic inflammation, preterm labor and premature rupture of membranes.

OBJECTIVE: Neutrophil defensins (HNP 1-3), bactericidal/permeability-increasing protein (BPI) and calprotectin (MRP8/14) are antimicrobial peptides stored in leukocytes that act as effector molecules of the innate immune response. The purpose of this study was to determine whether parturition, premature rupture of the membranes (PROM) and microbial invasion of the amniotic cavity (MIAC) are associated with changes in amniotic fluid concentrations of these antimicrobial peptides. STUDY DESIGN: Amniotic fluid was retrieved by amniocentesis from 333 patients in the following groups: group 1, mid-trimester with a subsequent normal pregnancy outcome (n = 84); group 2, preterm labor and intact membranes without MIAC who delivered at term (n = 36), or prematurely (n = 52) and preterm labor with MIAC (n = 26); group 3, preterm PROM with (n = 26) and without (n = 26) MIAC; and group 4, term with intact membranes in the absence of MIAC, in labor (n = 52) and not in labor (n = 31). The concentrations of HNP 1-3, BPI and calprotectin in amniotic fluid were determined by specific and sensitive immunoassays. Placentae of patients in both preterm labor with intact membranes and preterm PROM groups who delivered within 72 h of amniocentesis were examined. Non-parametric statistics, receiver-operating characteristic (ROC) curves and Cox regression models were used for analysis. A p value of < 0.05 was considered statistically significant. RESULTS: Intra-amniotic infection was associated with a significant increase in amniotic fluid concentrations of immunoreactive HNP 1-3, BPI and calprotectin in both women with preterm labor and intact membranes, and women with preterm PROM. Preterm PROM was associated with a significant increase in amniotic fluid concentrations of immunoreactive HNP 1-3, BPI and calprotectin. Preterm parturition was associated with a significant increase in amniotic fluid concentrations of immunoreactive HNP 1-3, BPI and calprotectin, while parturition at term was associated with a significant increase in amniotic fluid concentrations of immunoreactive HNP 1-3. Among patients with preterm labor and intact membranes, elevation of amniotic fluid HNP 1-3, BPI and calprotectin concentrations was associated with intra-amniotic inflammation, histological chorioamnionitis and a shorter interval to delivery. CONCLUSION: MIAC, preterm parturition and preterm PROM are associated with increased amniotic fluid concentrations of immunoreactive HNP 1-3, BPI and calprotectin. Moreover, elevated amniotic fluid concentrations of BPI, immunoreactive HNP 1-3 and calprotectin are associated with intra-amniotic inflammation, histological chorioamnionitis and shorter amniocentesis-to-delivery interval in patients presenting with preterm labor with intact membranes.

Amnion↗

[Behavior of the fibronectin content of the amniotic fluid].

Concentration of fibronectin in amniotic fluid was compared in early pregnancy and after 35th week of gestation. Content of amniotic fluid fibronectin between 15th and 20th week was significantly higher than after 35th week. Fibronectin-level was higher in amniotic fluid of female fetuses (15th-20th week) whereas concentration of protein in amniotic fluid of cases with chromosomal anomalies was declined (15th-21st week demonstrable.

Amniocentesis↗

Detection of phytoestrogens in samples of second trimester human amniotic fluid.

There is widespread concern that fetal exposure to hormonally active chemicals may adversely affect development of the reproductive tract. Therefore, the present study was performed to develop the necessary analytical methods and test the hypothesis that dietary phytoestrogens can be quantified in second trimester human amniotic fluid. Amniotic fluid samples (n=59) from women (n=53) undergoing routine amniocentesis between 15 and 23 weeks of gestation were analyzed by gas chromatography/mass spectrometric (GC/MS). Analytes included the phytoestrogens daidzein, genistein, formononetin, biochanin A, and coumestrol. Dietary phytoestrogens were quantified in 96.2% of second trimester amniotic fluid samples tested. The mean (+/- standard deviation (S.D.)) concentration of daidzein and genistein in amniotic fluid was 1.44 +/- 1.34 and 1.69 +/- 1.48 ng/ml with maximum levels of 5.52 and 6.54 ng/ml, respectively. Second trimester amniotic fluid contains quantifiable levels of dietary phytoestrogens and thus is a marker of mid pregnancy fetal exposure.

Adult↗

Significance of neutrophils and bacteria in the amniotic fluid of patients in labor.

Amniotic fluid specimens from 110 patients in labor were examined for neutrophils and bacteria. Patients with neutrophils in their amniotic fluid had significantly higher fever indices than patients with clear amniotic fluid. The highest fever indices were found in those patients who delivered by cesarean section after neutrophils were present in their amniotic fluid. Febrile morbidity was significantly reduced in a group of 24 such patients by giving prophylactic antibiotics.

Adult↗

Comparative study of proteinase inhibitors in human amniotic fluid and maternal serum.

Serum and amniotic fluid samples from five pregnant women were analyzed for different proteinase inhibitors by ion-exchange chromatography on DEAE-cellulose. Alpha-2 macroglobulin was found to be absent in amniotic fluid. Even though alpha-1 antichymotrypsin was identified in amniotic fluid, its concentration gradient between serum and amniotic fluid (20--60) was much higher than that of alpha-1 antitrypsin (8--20). Two forms of alpha-1 antitrypsin were identified in both the fluids. In pregnancy, the ratio of the two forms was altered in favour of the less anionic form compared to normal sera. The contribution of the heat stable proteinase inhibitor for total antitryptic activity in amniotic fluid was more than in serum. The observation that urine samples from immature infants had higher heat stable inhibitory activity than urine samples from normal infants suggests that the heat stable inhibitor in amniotic fluid may arise from fetal kidney.

Amniotic Fluid↗

[Submicroscopic structure of amniotic fluid cells].

Submicroscopic examination of amniotic fluid cells in the second trimester of pregnancy revealed that the cells are from the morphological aspect a very heterogeneous population, comprising vital and degenerated cells the ultrastructure of which rules out the possibility of cultivation of cells of foetal as well as of maternal origin. As to degenerated cells, the authors identified circular cells with a granular cytoplasm and nucleus originating from the urogenital or digestive tract of the foetus. Furthermore cells with a process and segmented or fragmented pycnotic nucleus derived from granulocytes and macrophages of maternal origin. Also circular cells of the periderm with short microvilli and advanced regressive changes of the nucleus and cytoplasm are degenerated. Among non-vital elements also anuclear completely keratinized cells of the stratum corneum originating from the skin of the maternal abdomen can be included. As to vital elements, the amniotic fluid contains cells of the amniotic ectoderm which are large, have numerous microvilli, a dense margin and a network of filaments in the cytoplasm. They are the most numerous cells. Other vital elements in amniotic fluid include granulocytes and macrophages with a typical ratio of lyzosomes. Both are considered elements of maternal origin. Maternal origin is assumed also in fibroblasts which along with collagen particles may penetrate into the aspirating needle. From the results ensues that the cells in amniotic fluid are not a homogeneous population of unequivocally foetal origin and that a better technique of collection of samples and cultivation must be developed.

Amniotic Fluid↗

Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume.

Adequate amniotic fluid (AF) volume is maintained by a balance of fetal fluid production (lung liquid and urine) and resorption (swallowing and intramembranous flow). Because fetal urine is the principle source of AF, alterations in urine flow and composition directly impact AF dynamics. Intra-amniotic 1-desamino-8-D-arginine vasopressin (DDAVP) is rapidly absorbed into fetal plasma and induces a marked fetal urinary antidiuresis. To examine the effect of intra-amniotic- DDAVP-induced fetal urinary responses on AF volume and composition, six chronically prepared ewes with singleton fetuses (gestation 128 +/- 2 days) were studied for 72 h after a single intra-amniotic DDAVP (50-microgram) injection. After DDAVP, fetal urine osmolality significantly increased at 2 h (157 +/- 13 to 253 +/- 21 mosmol/kg) and remained elevated at 72 h (400 +/- 13 mosmol/kg). Urinary sodium (33.0 +/- 4.5 to 117.2 +/- 9.7 meq/l) and chloride (26.0 +/- 2.8 to 92.4 +/- 8.1 meq/l) concentrations similarly increased. AF osmolality increased (285 +/- 3 to 299 +/- 4 mosmol/kg H2O), although there was no change in fetal plasma osmolality (294 +/- 2 mosmol/kg). Despite a 50% reduction in fetal urine flow (0.12 +/- 0.03 to 0.05 +/- 0.02 ml.kg-1.min-1 at 2 h and 0.06 +/- 0.01 ml.kg-1.min-1 after 72 h), AF volume did not change (693 +/- 226 to 679 +/- 214 ml). There were no changes in fetal arterial blood pressures, pH, PCO2, or PO2 after DDAVP. We conclude the following. 1) Intra-amniotic DDAVP injection induces a prolonged decrease in fetal urine flow and increases in urine and AF osmolalities. 2) Despite decreased urine flow, AF volume does not change. We speculate that, in response to DDAVP-induced fetal oliguria, reversed intramembranous flow (from isotonic fetal plasma to hypertonic AF) preserves AF volume.

Adaptation, Physiological↗

Amniotic fluid and placental stem cells.

Human amniotic fluid has been used in prenatal diagnosis for more than 70 years. It has proven to be a safe, reliable, and simple screening tool for a wide variety of developmental and genetic diseases. However, there is now evidence that amniotic fluid may have more use than only as a diagnostic tool and may be the source of a powerful therapy for a multitude of congenital and adult disorders. A subset of cells found in amniotic fluid and placenta has been isolated and found to be capable of maintaining prolonged undifferentiated proliferation as well as able to differentiate into multiple tissue types encompassing the three germ layers. It is possible that in the near future, we will see the development of therapies using progenitor cells isolated from amniotic fluid and placenta for the treatment of newborns with congenital malformations as well as of adults, using cryopreserved amniotic fluid and placental stem cells. In this chapter, we describe a number of experiments that have isolated and characterized pluripotent progenitor cells from amniotic fluid and placenta. We also discuss various cell lines derived from amniotic fluid and placenta and future directions for this area of research.

Adult Stem Cells↗

Inhibition of binding of bacteria to amniochorionic membranes by amniotic fluid.

The immunological composition of amniotic fluids is shown to be of such a lower order of activity that its role in fetal protection may be limited. Also, amniotic fluids were found not to have classical antibiotic activity. Amniotic fluids (25/31), however, were found to inhibit, by 27.5% to 88.2%, three target bacteria from binding to discs of amniochorionic membranes. This inhibition is also demonstrable with the monosaccharides alpha-D(+)-fucose, D(+)-galactose, alpha-D-glucose, alpha-D-lactose and bovine serum albumin-lactose conjugate, whereas other glycoconjugates enhanced bacterial binding. This demonstrates that the test bacteria bind to the amniochorionic membranes using bacterial lectins. In intraamniotic infection bacterial lectins may be complexed by amniotic fluid glycoconjugates which prevent the bacteria from binding to the amniochorionic membranes. This would explain asymptomatic infection and in the absence or reduced levels of the glycoconjugates the bacteria would bind to the amniochorionic membranes giving rise to symptomatic infection.

Amnion↗

Amniotic fluid matrix metalloproteinase-9 and interleukin-6 in predicting intra-amniotic infection.

OBJECTIVE: To assess the potential role of amniotic fluid (AF) matrix metalloproteinase-9 and interleukin-6 in predicting intra-amniotic infection. METHODS: Eighty-four women with singleton gestations with preterm contraction, preterm labor, preterm premature rupture of membranes, or clinical suspicion of intra-amniotic infection were studied. Amniotic fluid was obtained by transabdominal amniocentesis before starting any treatment. Intra-amniotic infection was defined as the presence of a positive AF culture. Amniotic fluid glucose concentration, leukocytes, matrix metalloproteinase-9, and interleukin-6 were determined. RESULTS: Amniotic fluid matrix metalloproteinase-9 and interleukin-6 levels were significantly higher in women with intra-amniotic infection than in those without. With intra-amniotic infection, levels of matrix metalloproteinase-9 significantly correlated with interleukin-6 (r = 0.813, P <.001). Each of matrix metalloproteinase-9 and interleukin-6 significantly correlated with AF leukocytes and inversely correlated with AF glucose. Using AF cutoff levels of 13.6 ng/mL for matrix metalloproteinase-9 and 11.4 ng/mL for interleukin-6, the sensitivity, specificity, and positive and negative predictive values for diagnosing intra-amniotic infection were 77% versus 73%, 100% versus 79%, 100% versus 61%, and 90% versus 86%, respectively. Combining AF matrix metalloproteinase-9 with interleukin-6 slightly improved the sensitivity and the negative predictive values in diagnosing intra-amniotic infection. CONCLUSIONS: Amniotic fluid matrix metalloproteinase-9 and interleukin-6 are significantly elevated in women with intra-amniotic infection. Amniotic fluid matrix metalloproteinase-9 is an accurate biochemical marker in predicting intra-amniotic infection with better sensitivity, specificity, and positive and negative predictive values than interleukin-6.

Adolescent↗

Normal ultrasonic evaluation of amniotic fluid in low-risk patients at term.

OBJECTIVE: To study women at the time of admission to the labor and delivery unit to determine which type of ultrasonographic assessment of the amniotic fluid--amniotic fluid index (AFI), single deepest vertical pocket (DVP) or amniotic fluid distribution (AFD)--had the greatest clinical utility in predicting labor complications. STUDY DESIGN: Patients not at term, with a nonvertex presentation, or with ruptured membranes, polyhydramnios, or known maternal or congenital abnormalities were excluded. We included 266 low-risk pregnant women admitted for labor. Medical charts were reviewed for documentation of meconium-stained amniotic fluid (Mec), cesarean section (C/S) for fetal indications and admissions to the neonatal intensive care unit (NICU). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for AFI, DVP and AFD were calculated in relation to the three outcome variables. Positive findings were defined as: AFI < 5.0, DVP < 2.5 cm and AFD, sum of the two lower quadrants of the AFI with a lower value than the sum of the two upper quadrants. RESULTS: Mec was documented in 56 patients (21%), 13 patients (4.8%) had a C/S for fetal indications, and 4 infants (1.5%) were admitted to the NICU. Abnormal AFI was detected in 35 patients (13%), abnormal DVP in 38 patients (14%) and abnormal AFD in 117 patients (44%). PPV and NPV for prediction of Mec, C/S and NICU were: Mec 31% and 80% for AFI, 26% and 80% for DVP; 31% and 91% for AFD; C/S 8.6% and 95% for AFI, 5% and 95% for DVP; 8.6% and 100% for AFD and NICU, 0% and 98% for AFI, 0% and 95% for DVP, and 2.7% and 99% for AFD. CONCLUSION: Normal ultrasonographic values for AFI and AFD are associated with a very low risk of labor complications.

Amniotic Fluid↗

Amniotic fluid index measurements during pregnancy.

Amniotic fluid volume assessment has become an important part of antepartum fetal surveillance. The amniotic fluid index (AFI), or four-quadrant technique, has been suggested for this purpose. While previous reports have outlined this technique and correlated the results with pregnancy outcome, none have reviewed the changes in AFI throughout pregnancy. We studied AFI changes from 11 through 43 weeks' gestation. As part of the entry criteria, only patients with good dates were evaluated. The AFI was determined by the summation of the vertical diameter of the largest pocket in each of the four quadrants. All amniotic fluid studies were conducted using real-time linear array B-scan. During the study period, 197 patients with good dates confirmed clinically and sonographically underwent 262 AFI assessments. From 11 to 26 weeks the AFI rose progressively. Thereafter until term, the AFI remained approximately 16.2 +/- 5.3 cm. After 38 weeks the AFI appeared to gradually decline. Data obtained from this study population corroborate previously defined normal amniotic fluid volumes. These results also suggest that serial measurements of the AFI may be an effective means of assessing fetal status throughout pregnancy.

Amniotic Fluid↗

Amniotic fluid embolism during caesarean section.

Amniotic fluid embolism occurs rarely but is a leading cause of maternal mortality. A high index of clinical suspicion is necessary to make an early diagnosis to reduce morbidity and mortality. We report a non-fatal case of amniotic fluid embolism occurring during a caesarean section, with special emphasis on the mode of development and diagnosis. The initial presentation of this syndrome was a coagulopathy, followed by the usual complications of massive bleeding. Although non-specific, the diagnosis of amniotic fluid embolism was supported by the observation of amniotic fluid in the central venous blood as well as in the broncho-alveolar fluid.

Adult↗

Amniotic fluid white blood cell count: a rapid and simple test to diagnose microbial invasion of the amniotic cavity and predict preterm delivery.

The purpose of this study was to determine the value of amniotic fluid white blood cell count in the diagnosis of microbial invasion of the amniotic cavity. Amniotic fluid was retrieved by amniocentesis from 195 patients with preterm labor and intact membranes. Fluid was cultured for aerobic and anaerobic bacteria, as well as for mycoplasmas. The prevalence of a positive amniotic fluid culture was 12.8% (25/195). Patients with a positive amniotic fluid culture had a significantly higher median amniotic fluid white blood cell count than did patients with a negative amniotic fluid culture (median, 6 cells/mm3; range, 0 to 11,000 cells/mm3 vs median, 320 cells/mm3; range, 1 to 4480 cells/mm3; p less than 0.0001). An amniotic fluid white blood cell count greater than or equal to 50 cells/mm3 had a sensitivity of 80% (20/25), a specificity of 87.64% (149/170), a positive predictive value of 48.78% (20/41), and a negative predictive value of 96.75% (149/154) in the detection of a positive amniotic fluid culture for microorganisms. Although the sensitivity of an amniotic fluid white blood cell count (greater than or equal to 50 cells/mm3) in the detection of microbial invasion of the amniotic cavity was greater than that of the Gram stain of amniotic fluid (80% [20/25] vs 48% [12/25]; p less than 0.05), the specificity was lower (87.64% [149/170] vs 98.8% [168/170]; p less than 0.05). However, 88% (15/17) of all patients with an amniotic fluid white blood cell count greater than or equal to 50 cells/mm3 and a negative amniotic fluid culture had a spontaneous preterm delivery. We conclude that the amniotic fluid white blood cell count is a sensitive, simple, and inexpensive test for the detection of microbial invasion of the amniotic cavity. An elevated amniotic fluid white blood cell count is a risk factor for preterm delivery.

Adult↗

Search for the pathogenic fungi in amniotic fluid.

Intra-amniotic infection with Candida is rare but considers an etiological factor for preterm rupture of membranes (PROM). The aim of the study was the investigation of the mycotic invasion of the amniotic cavity in pregnant women with PROM and with intact fetal memranes. 170 women were included in two groups: I (n = 150)--women with intact membranes; II (n = 20)--women with PROM. Samples of amniotic fluid were cultured on Sabouraud's medium. Fungal strains were isolated also from vagina, oral cavity and rectum of women with PROM. Intraamniotic infections were absent both in women with PROM and with intact membranes. Candida strains were isolated from vagina, oral cavity, and rectum in the group of women with PROM. Coexisting of multifocal Candida infections in pregnant women with PROM indicates that in those cases mycologic diagnosics should be recomended.

Amniotic Fluid↗