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PubMed2004

Excess of amniotic fluid: pathophysiology, correlated diseases and clinical management.

The evaluation of amniotic fluid volume represents, together with the evaluation of fetal growth, one of the most important indicators of fetal wellbeing. Amniotic fluid is produced by fetal urines with small aliquots from fetal membranes and lung fluids. The main determinant of its turnover is fetal swallowing together with a small absorption through fetal skin and membranes. The pathologic conditions that lead to an excess of amniotic fluid are represented by excessive production or by a reduction of the physiologic turnover. The most frequent cause is gestational diabetes. This complication can be diagnosed in 2-3% of pregnancies, as a result of increased insulin resistance, most frequently found in association with risk factors such as high maternal BMI. Placental hormones, such as HPL, act indeed to increase insulin resistance and can therefore lead to post-prandial hyperglycemia in predisposed mothers. Maternal hyperglicemia leads in turn to fetal hyperglycemia and fetal hyperinsulinemia. Increased amniotic fluid volume is not a constant feature, being associated with the most severe cases, but its evaluation is very useful in the clinical management. The resulting increase in uterine volume, also related to accelerated fetal growth, is a potential cause of premature delivery, a severe complication also considering the delay in fetal lung maturation observed with fetal hyperinsulinemia. The evaluation of the degree of polyhydramnios has to be pursued by ultrasound. Precise diagnostic steps must be followed in order to rule out other potentially associated causes. Amongst these, malformations of the intestinal tract, such as hesophageal atresia, that are associated with decreased or absent fetal swallowing, must be considered. The clinical workout must therefore include an ultrasound evaluation of fetal morphology together with an oral glucose tolerance test. The therapeutic approach will be defined according to the definition of the underlying cause. Many cases will benefit from bedrest, tocolysis and induction of lung maturation.

Diabetes, Gestational↗
PubMed2004

Identification and sequencing of bacterial rDNAs in culture-negative amniotic fluid from women in premature labor.

Our objective was to identify bacterial species present in culture-negative but 16S rDNA-positive amniotic fluid samples from women in preterm labor. Amniotic fluid from 69 women in preterm labor was cultured and examined for the proinflammatory cytokine interleukin-6 (IL-6). Polymerase chain reaction technology was used to detect highly conserved bacterial ribosomal DNA sequences (16S rDNAs). As previously reported, 16S rDNAs were identified in 15 (94%) of 16 culture-positive amniotic fluid samples, in 5 (36%) of 14 culture-negative samples with elevated IL-6, and in 1 (3%) of 39 culture-negative samples with low IL-6 levels. Direct sequencing was performed of 16S rDNAs from the 5 culture-negative amniotic fluid specimens with elevated IL-6, followed by database searches and phylogenetic analyses. The bacterial sequences identified included: two Leptotrichia sanguinegens, one human oral bacterium A33, one Fusobacterium nucleatum, and one Ureaplasma urealyticum. Identification and sequencing of 16S rDNAs in amniotic fluid is a promising technique to identify bacterial species associated with elevated IL-6 levels in culture-negative amniotic fluid that may contribute to the etiology of premature labor.

Adult↗
PubMed1977

F prostaglandin levels in amniotic fluid in premature labour.

The concentration of prostaglandin F (PGF) in amniotic fluid was measured by radioimmunoassay in 27 patients admitted in premature labour. There was a strong correlation between PGF levels in amniotic fluid and both cervical dilatation (r = 0.81; P less than 0.001) and duration of labour (r = 0.79; P less than 0.001). Cervical dilatation greater than 7 cm was associated with levels exceeding 2000 pg/ml. When contractions were present for less than one hour, levels of PGF were below 50 pg/ml. Low levels of PGF were found in amniotic fluid from a separate group of three patients, of whom two had cervical incompetence. It is concluded that the onset of premature labour is not associated with elevated levels of PGF in amniotic fluid. During premature labour, concentrations rise to an extent comparable to that observed in labour at term.

Amniotic Fluid↗
PubMed1994

Amniotic fluid prostanoid concentrations increase early during the course of spontaneous labor at term.

OBJECTIVE: The purpose of this study was to determine whether amniotic fluid concentrations of prostanoids increase during spontaneous labor at term. STUDY DESIGN: Amniotic fluid was retrieved transabdominally from 168 patients in spontaneous labor and from 82 patients not in labor. Prostaglandin E2, prostaglandin F2 alpha, 13, 14-dihydro-15-keto-prostaglandin F2 alpha, thromboxane B2, and 6-keto-prostaglandin F1 alpha concentrations were measured with sensitive and specific radioimmunoassays previously validated for amniotic fluid. Statistical analysis was conducted with Kruskal-Wallis analysis of variance, followed by Dunn's test for multiple comparisons. RESULTS: (1) Amniotic fluid concentrations of all prostanoids were significantly higher in patients in early labor (cervical dilatation of < or = 3 cm) than in patients not in labor. (2) The magnitude of the increase in amniotic fluid prostanoid concentrations during early labor was significantly greater for prostaglandin F2 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha than for prostaglandin E2, thromboxane B2, and 6-keto-prostaglandin F1 alpha. (3) Patients in the active phase of labor with cervical dilatations between 4 and 7 cm did not have higher prostanoid concentrations than those in early labor (cervical dilatation of < or = 3 cm). (4) A significant increase in amniotic fluid concentrations of prostaglandin F2 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha was found in patients with advanced cervical dilatation (8 to 10 cm) in comparison with those in early labor (< 3 cm). CONCLUSION: Amniotic fluid prostanoid concentrations increase early during the course of spontaneous labor at term.

Amniotic Fluid↗
PubMed2005

External cephalic version with an amniotic fluid index < or = 10: a systematic review.

OBJECTIVE: To review the literature and evaluate the role of the amniotic fluid index (AFI) on the success of an external cephalic version (ECV). STUDY DESIGN: A computerized search of MEDLINE and Cochrane databases were conducted using 'breech', 'version', 'external cephalic version', 'amniotic fluid', and 'amniotic fluid index'. References from the identified publications were manually searched to identify additional relevant articles. Articles from 1987 to 2004 were included. RESULTS: Of the initial 33 articles discovered, only three remained after exclusions. These articles used different AFI ranges for 'borderline' or 'low-normal' fluid measurements and therefore could not be combined for analysis. All three studies demonstrated a lower success rate of ECV with lower amniotic fluid volume estimates (AFI 5-8, <10, or <8.6), although none reached statistical significance. CONCLUSION: Due to limited and dissimilar data, it is impossible to define the lower AFI threshold for an unsuccessful ECV compared with the success of a normal AFI. Although not statistically significant, an AFI <10 may correlate with lower success rates for an ECV.

Amniotic Fluid↗
PubMed1992

Morphological changes of Neisseria gonorrhoeae in amniotic fluid of pregnant women in their midtrimester.

Ten selected samples of amniotic fluid obtained through transabdominal amniocentesis from 10 pregnant women in their 17th-19th weeks of pregnancy were investigated for the survival of Neisseria gonorrhoeae in amniotic fluid. In 8 cases an antibacterial effect was observed with morphological changes comparable to the effect of benzylpenicillin. When N. gonorrhoeae was inoculated in amniotic fluid at 10(5)-10(7) cells/ml, it survived as an average 2 h longer than after inoculation of 10(2)-10(4) cells/ml. Electron microscopic pictures of gonococci taken after 2.6 and 24 h incubation in amniotic fluid correlated with the growth curves. Electron microscopically there were marked morphologic changes of N. gonorrhoeae, viz. vacuolar degeneration of their cytoplasm with a damage to the bacterial wall up to its complete destruction and lysis of the cell.

Amniotic Fluid↗
PubMed1987

Two immunoreactive binding proteins for insulin-like growth factors in human amniotic fluid: relationship to fetal maturity.

A binding protein for insulin-like growth factors (IGFs) has been purified from human amniotic fluid by IGF-I affinity chromatography and high performance reverse phase chromatography. This protein, with an apparent molecular mass of 28K nonreduced and 34K reduced, had an identical amino-terminus to a previously purified binding protein from amniotic fluid and to placental protein 12. The purified preparation (BP-28) bound both IGFs with high affinity [Ka, 6.55 +/- 2.24 (+/- SD) L/nmol for IGF-I and 3.23 +/- 1.05 L/nmol for IGF-II], with approximately 0.5 mol binding sites/mol BP-28 for either ligand. A 53K IGF-binding protein purified from human plasma (BP-53) did not cross-react in a RIA for BP-28, and BP-28 had less than 0.1% molar cross-reactivity in a RIA for BP-53. Human amniotic fluid reacted strongly in both assays. Fractionation of amniotic fluid samples by reverse phase chromatography showed that BP-28 and BP-53 immunoreactivities were present on separate proteins. In 40 third trimester amniotic fluid samples selected to cover a wide range of lecithin to sphingomyelin ratios, the mean concentrations of BP-28 and BP-53 were 37.6 +/- 17.6 (+/- SD) and 4.6 +/- 1.6 mg/L, respectively. Significant negative correlations were found between the levels of both BP-28 and BP-53 and the lecithin to sphingomyelin ratio, suggesting an association between the levels of both proteins and the degree of fetal maturity. A significant positive association was also found between the levels of BP-28 and BP-53. We conclude that the 28K IGF-binding protein from amniotic fluid, like the previously purified 53K binding protein, has high affinity for both IGF-I and IGF-II, that it coexists in amniotic fluid with BP-53 or a related protein, and that the levels of both proteins decline with increasing fetal maturity.

Amniotic Fluid↗
PubMed1987

Amniotic fluid volume assessment with the four-quadrant technique at 36-42 weeks' gestation.

An ultrasound approach was developed to identify normal amniotic fluid volume. The uterine cavity was divided into four quadrants. With the use of linear-array, real-time B-scanning, the vertical diameter of the largest pocket in each quadrant was measured. The sum of these four quadrants was used to provide a single number for the amniotic fluid volume and termed the amniotic fluid index. This approach is simple, requires little time and gives a semiquantitative estimate of amniotic fluid volume. Based on our observations, the normal amniotic fluid index in term gestation is 12.9 +/- 4.6 cm. Evaluation of the relationship between amniotic fluid volume and fetal outcome is under investigation.

Amniotic Fluid↗
PubMed1988

Labor and infection. II. Bacterial endotoxin in amniotic fluid and its relationship to the onset of preterm labor.

We have previously reported the detection of endotoxin in the amniotic fluid of patients with gram-negative intraamniotic infection. Endotoxin or lipopolysaccharide is a potent biologic product capable of inducing prostaglandin release from several cell types and, therefore, may be involved in the onset of human parturition in the presence of intraamniotic infection. This article describes a technique for the quantification of endotoxin in amniotic fluid. The method uses a computer-assisted quantification of the turbidimetric reaction between the Limulus amebocyte lysate and endotoxin. Serial dilutions of Escherichia coli endotoxin in culture-negative amniotic fluid were prepared, and the samples were run in the assay. Amniotic fluid was found to enhance the reaction, and a dilution of 1:20 was required for this biologic fluid to behave similarly to pyrogen-free water. The sensitivity of this kinetic turbidimetric technique in the detection of endotoxin in amniotic fluid was 40 pg/ml. This method was applied to the quantification of endotoxin concentration in amniotic fluid in 26 patients with intraamniotic infection and premature rupture of membranes. Patients in active labor had higher concentrations of endotoxin (median = 47,514 pg/ml) than nonlaboring patients (median = 635 pg/ml) (p less than 0.025). Therefore, women with preterm labor had a higher median concentration of endotoxin in amniotic fluid than patients who were not in labor.

Amniotic Fluid↗
PubMed1980

Comparison of amino acid concentrations in amniotic fluid from fetal neural tube defective and normal pregnancies.

Amniotic fluid collected during the second trimester of pregnancy was analysed for amino acid and protein concentrations. The composition of amniotic fluid from pregnancies complicated by fetal anencephaly or spina bifida was investigated for variance from normal amniotic fluid. In spina bifida the hydroxy amino acids were raised whilst the branched chain amino acids were lower in concentration. In anencephaly the total amino acid and the protein concentrations were raised, and a wider range of concentrations for most of the amino acids was apparent.

Amino Acids↗
PubMed1990

In vitro inhibition of esterase activity in amniotic fluid: comparison with bacterial cultures.

Assessment of leukocyte esterase activity in amniotic fluid for the rapid and reliable diagnosis of chorioamnionitis has been demonstrated previously. We compared in vitro inhibition of esterase activity in amniotic fluid with bacterial cultures to identify the origins of the specific esterases released by the infecting organisms. One hundred forty-one samples were tested (90 uninfected, 51 infected). Each sample was evaluated for Gram stain, cultures, and an in vitro esterase assay followed by ebelactone inhibition. Forty-two patients had positive amniotic fluid cultures. Ebelactone produced varying degrees of inhibition of esterase activity (range, 20% to 60%) in the uninfected samples and in those infected with gram-negative organisms. There was no inhibition in the samples infected with gram-positive organisms. Thus different groups of bacteria may elicit the production of different and specific esterases in infected amniotic fluid, as shown by the differences in in vitro inhibition.

Amniotic Fluid↗
PubMed1985

Quantitative determination of phosphatidylglycerol in amniotic fluid by enzymatic assay.

Phosphatidylglycerol (PG) was extracted from 54 human amniotic fluids for the assessment of fetal lung maturity. The PG values were derived from an enzymatic assay involving initial conversion of PG to glycerol by phospholipase C and alkaline phosphatase with subsequent analysis of the glycerol formed. This method proved to be reliable when compared with a method for two-dimensional thin layer chromatographic (2D TLC) analysis of amniotic fluid phospholipids. The results revealed that in all but one of 27 amniotic fluids in which no PG was detected by 2D TLC, enzymatic PG concentrations were less than or equal to 1.5 mumol/l and out of these, from 10 newborn infants delivered within 72 h of sampling, 4 developed respiratory distress syndrome (RDS). Conversely, in all but one of 27 amniotic fluids found to contain PG by 2D TLC, enzymatic PG concentrations were greater than 1.5 mumol/l and except for one subject from non-identical twins, no infants developed RDS.

Alkaline Phosphatase↗
PubMed1992

Use of quantitative amniotic fluid phosphatidylglycerol as a criterion for fetal lung maturation.

Phosphatidylglycerol (PG) in amniotic fluid was quantitatively measured by thin-layer chromatography (TLC) in 941 amniotic fluid samples and related to the presence or absence of respiratory distress syndrome (RDS) in neonates born within 7 days of the amniocentesis. In 639 case tests with PG 1 nmol/ml or more of amniotic fluid, there was no RDS. However, there were six cases of RDS associated with 109 tests of PG from 0 to less than 1 nmol/ml. These 109 tests would all have been reported as PG positive if PG were only qualitatively assessed on the TLC plate by the naked eye. The highest incidence of RDS occurred when PG was absent (23 RDS of 193 patients). Hence, this study suggests that quantitative analysis of PG determines a cutoff point of PG that eliminates false-positive PG assessments (1 nmol/ml in our laboratory). There was no difference in the levels of PG between males and females at equal gestational ages, but the incidence of RDS among male neonates was 2.4 times higher (p less than 0.05) than female neonates in the group with an immature amniotic fluid lecithin to sphingomyelin ratio and PG less than 1.0 nmol/ml.

Amniotic Fluid↗
PubMed1984

Glucocorticoids directly affect spectrophotometry of bilirubin in amniotic fluid.

Dexamethasone or prednisolone, added in vitro to bilirubin-containing amniotic fluid, produces a time-dependent decrease in the 450-nm absorbance of the pigment. Neither the chemical determination of bilirubin in amniotic fluid nor the lecithin/sphingomyelin ratio as determined by thin-layer chromatography is affected by these glucocorticoids. The effect probably is not a result of displacement of bilirubin from its binding sites on albumin, because the absorbance of a solution of crystalline bilirubin at 450 nm is unaffected by added bovine serum albumin. Light scattering of amniotic fluid increases slightly when dexamethasone is added, whether or not low concentrations of bilirubin (less than 1.6 mumol/L) are present. Thus the effect on absorbance evidently is not ascribable to supersaturation and formation of a colloidal sol of bilirubin particles. This direct interference of glucocorticoids with the spectrophotometry of bilirubin in amniotic fluid prompts cautious interpretation of such data as an index to the severity of hemolytic disease of the fetus, specifically in cases of Rhesus-isoimmunization that are being treated with glucocorticoids.

Amniotic Fluid↗
PubMed1980

Studies on the growth-inhibiting property of amniotic fluids from two United States population groups.

This study attempted to determine if lack of antimicrobial activity in amniotic fluid is the reason United States blacks have more amniotic fluid bacterial infection than whites. No significant interracial differences were found in a study of 111 fluids from whites and 56 fluids from blacks. It has been claimed that the phosphate:zinc ratio in amniotic fluid is an accurate predictor of antimicrobial activity. The present study found this often to be untrue. Amniotic fluids that lacked antimicrobial activity gained such activity when zinc was added, but the in vitro zinc levels required were usually higher than observed physiologic concentrations. Previous studies have claimed that antimicrobial activity first appears in the amniotic fluid in the third trimester of gestation. We found such activity in the majority of fluids by the end of the first trimester, with a Staphylococcus aureus indicator; in contrast, with Escherichia coli and Streptococcus agalactiae as test organisms, greater inhibition was observed after 35 weeks.

Amniotic Fluid↗
PubMed1980

Amniotic fluid bile acids in normal and pathologic pregnancy.

Radioimmunologic techniques were used to determine 2 primary bile acids (cholic and chenodeoxycholic acid) and 1 secondary bile acid (deoxycholic acid) from human amniotic fluid of healthy pregnant women and from patients with diabetes, toxemia, or intrahepatic cholestasis during pregnancy. In general, the mean bile acid concentrations in the amniotic fluid were very similar to those in the serum, although in paired samples from individual patients these 2 values did not correlate significantly. Very high levels of the 2 primary bile acids were measured from the amniotic fluid of patients with intrahepatic cholestasis. The mean values were about 70 times higher than those in the controls. Amniotic fluid cholic acid content was slightly elevated in diabetic and toxemic patients, too. Deoxycholic acid was consistently found in the amniotic fluid specimens, but there was no change in its concentration among the various groups. In this limited series of patients, no significant correlation was found between the bile acid concentrations in the amniotic fluid and signs of fetal distress at the time of amniocentesis, although the lowest maternal serum estriol and human placental lactogen values were associated with the highest amniotic fluid bile acid concentrations. The condition of the newborn infants did not correlate with amniotic fluid bile acid concentrations in any of the patient groups studied. It thus appears that high amniotic fluid bile acid content present a threat to the fetus, but further studies are needed to clarify this point.

Adult↗
PubMed2000

Human amniotic fluid lacks interleukin-2 and interleukin-15 but can interact with the beta-chain of the interleukin-2 receptor.

The present study investigated whether an explanation for the conflicting reports on the interleukin-2 (IL-2) status of amniotic fluid is due to the presence of IL-15 which shares biological activities with IL-2 and utilizes the IL-2 receptor beta-chain. Amniotic fluids from 45 normally progressing pregnancies between 14 and 16 weeks after the last menstrual period were assayed for IL-2 and IL-15 by bioassay and enzyme-linked immunosorbent assay (ELISA). The ability of amniotic fluids to induce cytotoxic T lymphoblastoid line-2 (CTLL-2) cell proliferation was demonstrated to be dependent upon bioassay culture conditions. In serum-free medium each amniotic fluid stimulated CTLL-2 proliferation with a mean level of IL-2-like bioactivity of 14.7 +/- 2.3 ng/ml but amniotic fluids failed to induce CTLL-2 proliferation in serum-supplemented medium. Treatment with neutralizing anti-IL-2 or anti-IL-15 antibodies failed to inhibit amniotic fluid-induced CTLL cell proliferation in serum-free medium, indicating a lack of IL-2 and IL-15 bioactivity. In contrast, treatment with anti-IL-2 receptor beta-chain antibody significantly reduced amniotic fluid-induced proliferation. The lack of IL-2 and IL-15 activity in amniotic fluids was confirmed using ELISA. Although high levels of IL-15 immunoactivity were detected in all samples, specificity controls showed a lack of specific IL-15 immunoactivity in amniotic fluid. Pretreatment of amniotic fluids with 100-500 ng/ml mouse immunoglobulin G abrogated IL-15 immunoactivity, indicating that amniotic fluid contains molecules binding to Fc regions of immunoglobulins and responsible for false ELISA positivity. These studies unequivocally show that amniotic fluid lacks IL-2 and IL-15 but can stimulate CTLL-2 cell proliferation via the IL-2 receptor beta-chain. The absence of IL-2 and IL-15 in normal mid-trimester amniotic fluid suggests that the cytokine profile of human pregnancy appears to be associated with a bias against type 1 cytokines within the feto-placental unit.

Amniotic Fluid↗
PubMed1982

[Studies on the intercompartmental relationship of PRL secretion during human pregnancy--maternal, fetal, and amniotic fluid PRL--(author's transl)].

Although it is well established that PRL is present in the maternal serum, fetal serum, and amniotic fluid during human pregnancy, the precise interrelationship among those three compartments is unknown. In order to elucidate the intercompartmental relationship, several experiments were undertaken. Results are as follows: 2. The concentration of amniotic fluid PRL was different from that of maternal or fetal serum PRL during gestation. 2. There was no correlation between amniotic fluid and maternal or cord serum PRL at delivery. 3. Although bromocriptine suppressed the secretion of maternal serum PRL abruptly, the concentration of amniotic fluid PRL remained unchanged after the administration of bromocriptine at mid-gestation. 4. Analysis of molecular size of PRL by Sephadex G-100 column gel filtration revealed that the elution profiles of maternal serum PRL, fetal serum PRL, and amniotic fluid PRL differed from one another and furthermore, they were similar to those of adult pituitary PRL, fetal pituitary PRL, and decidual PRL, respectively. 5. PRL which was secreted from decidua could transfer to amniotic cavity across the fetal membrane. 6. Decidual PRL and amniotic fluid PRL have a biological activity. These results suggest that three compartments of PRL secretion during human pregnancy are independent each other and, furthermore, possible origin of amniotic fluid PRL is decidua.

Amniotic Fluid↗