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PubMed1981

Amniotic fluid acetylcholinesterase electrophoresis as a secondary test in the diagnosis of anencephaly and open spina bifida in early pregnancy. Report of the Collaborative acetylcholinesterase Study.

Fifteen centres collaborated in a study to determine the value of amniotic fluid acetyl cholinesterase (AChE) electrophoresis in the diagnosis of fetal open neural-tube defects (NTDs) between 13 and 24 weeks of gestation among women with positive amniotic fluid alpha-fetoprotein (AFP) results. Pregnancies with positive amniotic fluid AFP results were identified from about 34 000 tested; on average they had values greater than the 99.6th percentile for non-NTD pregnancies. Amniotic fluid samples were available from 1099 pregnancies with positive AFP results, and the percentages which yielded positive AChE results were as follows: anencephaly 99.6% (476/478); open spina bifida 99.4% (333/335); non-NTD pregnancies (i) without serious malformation and not ending in miscarriage 6% (8/125), (ii) without serious malformation but ending in miscarriage 47% (34/73), (iii) exomphalos 75% (47/63), (iv) congenital nephrosis 0% (0/11), (v) other serious malformations 50% (7/14). The gel-AChE test was thus found to be very effective when applied to amniotic fluid samples with positive AFP results, substantially reducing the number of false positives with only a very small loss in the detection of open neural-tube defects. Among women with positive amniotic fluid AFP results, the risk of having a fetus with an open NTD compared to having one without a serious malformation or a miscarriage is raised about 16-fold if the AchE test is also positive. The actual risk will depend on the birth prevalence and the reason for amniocentesis. For example, in the U.K. the risk of open spina bifida (expressed as an odds ratio) when both the amniotic fluid AFP result and the gel AChE results are positive would be as follows for women referred for amniocentesis in different categories; approximately 288:1 for those referred because of single raised serum AFP level (greater than or equal to 2.5 time the normal median at 16-18 weeks of gestation, 80:1 for women referred because of having previously had an infant with an NTD, and 8:1 for women referred for other reasons. It the amniotic fluid sample is stained with blood which is mainly fetal in origin, the corresponding odds are much lower (36:1, 10:1, and 1:1 respectively): if it is not blood-stained or is stained mainly with maternal blood, they are higher (954:1, 265:1, and 26:1 respectively).

Acetylcholinesterase↗
PubMed1980

Pulmonary lamellar bodies in human amniotic fluid: their relationship to fetal age and the lecithin/sphingomyelin ratio.

We investigated the appearance of pulmonary lamellar bodies (LBs) in human amniotic fluid as a function of fetal age. We also studied their relationship to the lecithin/sphingomyelin (L/S) ratio and to the results of the rapid surfactant test (RST). LBs observed in amniotic fluid generally ranged in diameter from 1.5 to 2.0 mu and were seen as single structures or in clusters. When patients were grouped by gestational age, there was a significant difference (P less than 0.001) in the distribution of amniotic fluid LBs. No LBs were observed in amniotic fluid before 26 weeks' gestation, but 50% of specimens at 28 to 32 weeks' gestation and 85% of specimens at term had LBs. Patients with amniotic fluid LBs had higher L/S ratios and intermediate or mature RST values when compared to patients without LBs, but a statistically significant relationship between the presence of LBs and the L/S ratio or RST was not found. We conclude that qualitative examination of amniotic fluid LB content by conventional electron microscopy is unlikely to reflect fetal lung maturation in a precise manner. However, direct quantification of LBs may provide a more specific index of fetal lung maturity and the risk of respiratory distress syndrome.

Amniotic Fluid↗
PubMed1987

Amniotic fluid beta-endorphin levels and labor.

To define the relationship between amniotic fluid concentrations of beta-endorphin immunoreactivity and onset of parturition, we measured this opioid in samples obtained during cesarean section at term. A total of 27 women were studied, 14 without labor and 13 in early labor. Mean (+/- SE) amniotic fluid beta-endorphin levels were significantly lower in patients in labor than in those not in labor (3.2 +/- 0.05 versus 8.4 +/- 1.0 fmol/mL). The mean beta-endorphin level (21.1 +/- 4.2 fmol/mL) in other amniotic fluid samples obtained during the second trimester of pregnancy was significantly higher than mean values at term. These differences in amniotic fluid beta-endorphin levels may support the theory of an opioid mechanism involved in parturition.

Adult↗
PubMed1992

Amniotic fluid volume assessment: comparison of ultrasonographic estimates versus direct measurements with a dye-dilution technique in human pregnancy.

OBJECTIVE: The purpose of our study was to compare the accuracy of clinical ultrasonographic techniques of amniotic fluid volume assessment with a dye-dilution technique. STUDY DESIGN: We compared amniotic fluid volume as measured by ultrasonographic techniques with a dye-dilution method in 50 women undergoing amniocentesis during the third trimester. Thirteen separate ultrasonographic techniques, including the amniotic fluid index, were evaluated with regression analysis. RESULTS: Amniotic fluid volumes as determined by dye-dilution ranged between 129 and 4444 ml. The amniotic fluid index overestimated the actual volume by as much as 88.7% at lower volumes and underestimated the actual volume by as much as 53.9% at higher volumes. CONCLUSIONS: Differences in measurement error between the other ultrasonographic methods and the amniotic fluid index did not appear to be sufficient to warrant changes in current clinical practice. A major source of error in ultrasonographic amniotic fluid volume assessment is that one-dimensional measurements are used to estimate the volume of a complex, three-dimensional object.

Amniotic Fluid↗
PubMed1985

Gastric inhibitory polypeptide (GIP) concentration in human amniotic fluid.

Several studies report that placenta and amniotic fluid (AF) may be a source of many peptide hormones. Although the presence of gastric inhibitory polypeptide (GIP) in amniotic fluid has not been described, it is present in the fetal gut. In this study we report the presence of insulin and GIP in human AF of normal and diabetic pregnancies. GIP concentrations in the AF collected two hours after an arginine tolerance test (ATT), at 34-36 weeks of gestation, were evaluated in 8 normal and 53 diabetic pregnant women. GIP was found in all samples of AF. The mean AF-GIP concentrations were 133 +/- 19 pmol/l in controls and 111 +/- 6 pmol/l in the diabetics, being the GIP values of the diabetics belonging to White Class B significantly lower than those of normals (99 +/- 10 vs 133 +/- 19 pmol/l). The GIP/IRI molar ratio was significantly lower in the diabetics than in controls (1.2 +/- 0.2 vs 2.5 +/- 0.4); moreover the GIP/IRI molar ratio was significantly higher in AF collected from diabetic pregnant women who delivered overweight infants than in AF of normal weight infants or controls. This finding would suggest a negative feedback mechanism between GIP and insulin in fetus.

Adult↗
PubMed1991

Early amniocentesis: alphafetoprotein levels in amniotic fluid, extraembryonic coelomic fluid and maternal serum between 8 and 13 weeks.

OBJECTIVE: The aim was to establish a normal range of alphafetoprotein (AFP) concentrations in amniotic fluid from 8 to 12 weeks gestation, and to determine any difference between AFP levels in amniotic fluid and extraembryonic coelomic fluid. DESIGN AND SUBJECTS: 150 women had a transvaginal ultrasound guided amniocentesis before termination of an apparently normal first trimester pregnancy. Separately identified samples of amniotic fluid and extraembryonic coelomic fluid were obtained and assayed by radioimmunoassay for AFP. RESULTS: In amniotic fluid, very high levels of AFP were present at 8 weeks, levels falling rapidly up to 10 weeks after which there was a slight rise. Thus over the period 8 to 10 weeks, there was a significant inverse correlation between amniotic fluid AFP and gestational age (r = 0.67; P less than 0.001). In extraembryonic coelomic fluid, by contrast there was no trend in AFP relative to gestational age. CONCLUSIONS: The rapidly changing levels of AFP from 8 to 10 weeks as well as the small volume of the amniotic cavity makes the use of amniocentesis impracticable before 11 weeks gestation. The lack of any relation between AFP levels in amniotic fluid and extraembryonic coelomic fluid emphasises the importance of identifying the site of amniocentesis in the first trimester.

Amniotic Fluid↗
PubMed1999

Perinatal outcome and amniotic fluid index in the antepartum and intrapartum periods: A meta-analysis.

OBJECTIVE: Our purpose was to perform a meta-analysis of studies on the risks of cesarean delivery for fetal distress, 5-minute Apgar score <7, and umbilical arterial pH <7.00 in patients with antepartum or intrapartum amniotic fluid index >5.0 or <5.0 cm. STUDY DESIGN: Using a MEDLINE search, we reviewed all studies published between 1987 and 1997 that correlated antepartum or intrapartum amniotic fluid index with adverse peripartum outcomes. The inclusion criteria were studies in English that associated at least one of the selected adverse outcomes with an amniotic fluid index of </=5.0 cm versus >5.0 cm. Contingency tables were constructed for each study, and relative risks and standard errors of their logs were calculated. Fixed-effects pooled relative risks were calculated for groups of studies that were homogeneous, whereas random-effects pooled relative risks were calculated for significantly heterogeneous groups of studies. RESULTS: Eighteen reports describing 10,551 patients met our inclusion criteria. An antepartum amniotic fluid index of </=5.0 cm, in comparison with >5.0 cm, is associated with an increased risk of cesarean delivery for fetal distress (pooled relative risk, 2.2; 95% confidence interval, 1.5-3.4) and an Apgar score of <7 at 5 minutes (pooled relative risk, 5.2; 95% confidence interval, 2.4-11.3). An intrapartum amniotic fluid index of </=5.0 cm is also associated with an increased risk of cesarean delivery for fetal distress (pooled relative risk, 1.7; 95% confidence interval, 1.1-2.6) and an Apgar score <7 at 5 minutes (pooled relative risk, 1.8; 95% confidence interval, 1.2-2.7). A poor correlation between the amniotic fluid index and neonatal acidosis was noted in the only study that examined this end point. More than 23,000 patients are necessary to demonstrate that the incidence of umbilical arterial pH <7.00 is 1.5 times higher among those with oligohydramnios in labor than among those with adequate amniotic fluid index (alpha = 0.05; beta = 0.2) CONCLUSIONS: An antepartum or intrapartum amniotic fluid index of </=5.0 cm is associated with a significantly increased risk of cesarean delivery for fetal distress and a low Apgar score at 5 minutes. There are few reports linking amniotic fluid index and neonatal acidosis, the only objective assessment of fetal well-being. A multicenter study with sufficient power should be undertaken to demonstrate that a low amniotic fluid index is associated with an umbilical arterial pH <7.00.

Acidosis↗
PubMed2005

Amniotic fluid index and fetal bladder outlet obstruction. Do we really need more?

PURPOSE: With the constant advances in technology and expertise of prenatal diagnosis, necessity of early counseling in cases of bilateral obstructive uropathy has become of paramount importance. To better evaluate fetal renal function new biochemical (serum and urine) fetal markers have been introduced in the literature. However, they are only available at select centers and always requiring an invasive approach. Furthermore, paucity of normal controls sometimes makes interpretation of results difficult. Owing to this growing interest towards biochemical evaluation of fetal renal function, assessment of amniotic fluid, which is mostly expression of fetal urination, has progressively fallen into disrepute, and studies comparing the amount of amniotic fluid with renal function are scant. MATERIALS AND METHODS: In a 3-year period 28 cases of bilateral obstructive uropathy were seen prenatally at the Artemisia Medical Center. All cases were initially reviewed at 17 to 20 weeks of gestation when a distended fetal bladder with thickened wall and enlarged kidneys were visualized. At the same time ultrasonographic assessment of amniotic fluid was performed by calculating the amniotic fluid index. An amniotic fluid index less than the 25th percentile was considered below average and an index less below the 5th percentile was considered oligohydramnios, whereas an index between 50th and 75th percentiles was considered normal. All cases were subsequently evaluated for renal function up to age 1 year. Impaired renal function was defined as a serum creatinine greater than 1.2 mg/dl before age 1 year. RESULTS: Of the 28 cases 18 had an index of oligohydramnios (group 1) and 10 had a normal index (group 2). No significant variations were observed in amniotic fluid index at repeated consultations throughout pregnancy. Two cases in group 1 and 1 case in group 2 were lost to followup while in the other group 1 cases intrauterine death occurred. Bilateral obstructive uropathy was confirmed in all instances after birth as valves in 18 cases and urethral atresia in 3. Of the 12 surviving group 1 cases there were 3 neonatal deaths from severe lung hypoplasia, and in the remaining 9 cases mean serum creatinine at each evaluation before age 1 year was 1.3 +/- 0.2 mg/dl. All patients in group 2 survived with a mean serum creatinine at each evaluation of 0.6 +/- 0.1 mg/dl (p <0.05). CONCLUSIONS: Despite widespread use of prenatal biochemistry, evaluation of amniotic fluid by the amniotic fluid index remains a reproducible and inexpensive method to predict renal function in cases of bilateral obstructive uropathy of any origin. It retains its validity not only in severe, but also in milder reductions. Conversely, intact amniotic fluid mostly invariably predicts normal renal function at long-term evaluation. For a better understanding of the disease such information is to be promptly conveyed to the prospective parents at each prenatal consultation.

Female↗
PubMed1981

Maternal smoking and elevation of catecholamines and metabolites in the amniotic fluid.

To assess the effect of maternal smoking on fetal adrenergic activity, simultaneous measurements in amniotic fluid of the parent catecholamines, dopamine (DA), norepinephrine (NE), and epinephrine (E), as well as the specific intraneuronal deaminated metabolites of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and of NE, 3,4-dihydroxyphenylglycol (DOPEG), were made by radioenzymatic assay. In the second trimester, a significant (p less than 0.002) and selective elevation of the mean DOPEG concentration was noted in the amniotic fluid of smokers (N = 8) as compared to nonsmokers (N = 36). In the third trimester, significant elevations were found in the mean amniotic fluid concentration of E (p less than 0.0002) and NE (p less than 0.0005), as well as DOPEG (p less than 0.0002), of smokers (n = 12) when compared to nonsmokers (N = 12). There were no significant differences in amniotic fluid concentrations of DA and its deaminated metabolite DOPAC. Since compartmentalization of catecholamines exist between the maternal and fetal circulations, the elevated levels of NE, E, and DOPEG in the amniotic fluid of smokers suggests fetal adrenergic activation as a result of fetal hypoxia and/or by a direct effect of nicotine on the fetal adrenergic system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1984

Detection of novel fetal polypeptides in human amniotic fluid using two-dimensional gel electrophoresis.

We compared the two-dimensional polypeptide pattern of donor-matched samples of mid-gestational amniotic fluid and maternal plasma to identify fetally-derived polypeptides in the amniotic fluid. Ten major polypeptide groups, ranging in molecular mass from 14.6 to 225 Kilodaltons (K), were consistently present in amniotic fluid that were not detected in maternal plasma. Three of these polypeptide complexes have been identified: one is alphafetoprotein, the second is a cellular form of fibronectin, and the third is beta 2-microglobulin. We searched for the remaining seven polypeptides in fetal serum and urine to confirm their fetal origin. Urine contained two polypeptides at 30.5K and 25.5K with mobilities identical to species found in amniotic fluid; the 25.5K polypeptide was also present in cord serum. Possible sources for the remaining 5 components may be the fetal respiratory and gastrointestinal tracts, integument, membranes (amnion and chorion) or the uterus. In addition, developmental changes in amniotic fluid polypeptides were studied by comparing samples obtained at mid-gestation and at term. Three proteins characteristic of mid-gestational amniotic fluid with masses of 185.8K, 38.2K and 25.4K were not detected or were present only at trace levels at term; and new polypeptide groups at approximately 51K, and 18K were observed in late gestation.

Adult↗
PubMed1997

The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: the effect of operator experience and ultrasound interpretative technique.

The objective of this study was to evaluate the effect of operator experience and ultrasound interpretation technique on the accuracy of ultrasound estimates of amniotic fluid volume. Ultrasound evaluation was carried out by an obstetric resident, a nurse sonographer, a maternal-fetal medicine fellow, and a maternal-fetal medicine staff member to subjectively estimate (visual interpretation without sonographic measurements) amniotic fluid volume in 63 pregnancies. Amniotic fluid volume was also evaluated using ultrasound measurements based on the largest vertical pocket technique, the amniotic fluid index, and the two-diameter pocket method. The accuracy of these ultrasound estimates was assessed by comparing the ultrasound results to actual amniotic fluid volume as determined by a dye-dilution technique. For analysis, amniotic fluid volumes were classified as oligohydramnios, normal, or hydramnios using established volumetric criteria for singleton pregnancies. Subjective estimates ranged from 65% to 70% correct and did not differ by operator experience except for the more accurate diagnosis of hydramnios by the maternal-fetal medicine staff. The three sonographic measurements were similar in overall accuracy (59-67%). The two-diameter pocket method was, however, significantly more accurate in identifying oligohydramnios. It appears that neither operator experience nor sonographic technique greatly affects the accuracy of ultrasound estimates of amniotic fluid volume.

Adolescent↗
PubMed1989

Trophic effect of amniotic fluid on cultured fetal gastric mucosal cells.

This study examines the hypothesis that the growth and development of fetal gastric epithelial cells is critically dependent on the presence of trophic factors in amniotic fluid. Fetal gastric epithelial cells (predominantly parietal cells) were grown in culture in the presence of graded concentrations of rabbit amniotic fluid, fetal bovine serum, or a control solution containing the nutrients specific to amniotic fluid. After 7 days, cells were harvested and growth was assessed by cell counts and DNA contents. Amniotic fluid stimulated growth of these cultured cells with a potency similar to that of fetal bovine serum. Cell growth was significantly enhanced by amniotic fluid at each dose tested, when compared to the appropriate nutrient control group. Cell growth could not be maintained in the absence of amniotic fluid or fetal bovine serum. We conclude that amniotic fluid contains factors which are trophic to the growth of cultured fetal gastric epithelial cells. The nature of these factors remains to be determined.

Amniotic Fluid↗
PubMed1981

Sedimentation of lung-derived phospholipid during low-speed centrifugation of amniotic fluid.

In most methods proposed for the assessment of fetal lung maturity, amniotic fluid is subjected to a preliminary low-speed centrifugation in an attempt to separate whole cells and cell debris from lung-derived surfactant phospholipid (lamellar body phospholipid). However, because lamellar body phospholipid is present in amniotic fluid in a membranous or particulate form, it is also partly sedimented by this procedure. The sedimentation of total phospholipid and lamellar body phospholipid by low-speed centrifugation has been quantitated for 49 samples of amniotic fluid from pregnancies of 30--41 weeks gestation. Isopycnic density-gradient centrifugation in a small air-driven ultracentrifuge was used to isolate lamellar body fractions from whole and centrifuged amniotic fluid. Centrifugation for 5 min at 1000 x g removed 0--70% of total phospholipid or lamellar body phospholipid, the mean values being 34 or 29%, respectively. There was an appreciable increase in lamellar body phospholipid relative to total phospholipid as a result of centrifugation in only 51% of the samples. In general, the effects of centrifugation were not related to gestational age of the fetus or the state of maturity of its lungs.

Amniotic Fluid↗
PubMed1979

Prenatal diagnosis of Tay-Sachs disease: studies on the reliability of hexosaminidase levels in amniotic fluid.

Measurement of hexosaminidase A activity in amniotic fluid was found to be a reliable diagnostic test in the prenatal diagnosis of Tay-Sachs disease. Including normal control specimens, analysis of 39 amniotic fluid samples have correctly predicted the condition of the fetus or, in pregnancies not yet come to term, have been in agreement with results from cultured cell extracts. In each case where both fluid and cultured cell extracts were analyzed, the results were in agreement. Analysis were performed by means of Cellogel, starch gel electrophoresis, polyacrylamide gel electrophoresis, or heat inactivation.

Amniotic Fluid↗
PubMed1984

Insulin-like growth factors in amniotic fluid.

The concentrations of insulin-like growth factors I and II (IGF-I and IGF-II) in amniotic fluid were determined by specific immunoassays in 58 women. IGF-I concentrations were constant throughout gestation at approximately 20 ng/ml; the mean IGF-II concentration was 114 +/- 13 (+/- SE) ng/ml at the earliest period of gestation studied and remained unchanged at 26 to 33 weeks despite a greater than 50% decrease in amniotic fluid total protein. A precipitous decrease in IGF-II concentration occurred at term which was not explainable by alterations in total amniotic fluid protein concentration. The concentrations of IGF-I and IGF-II in amniotic fluid did not correlate with concentrations of these factors in maternal serum (r = 0.08 and 0.09, respectively). [125I]IGF-I and [125I]IGF-II, after incubation with amniotic fluid, bound to a 40-45 K protein (or proteins). A carrier protein of greater mol wt, as in serum, was not detected. These findings indicate that there is dynamic control of IGF in amniotic fluid during normal pregnancy.

Amniotic Fluid↗
PubMed1978

Determination of disaturated lecithin in rhesus monkey amniotic fluid as an index of fetal lung maturity.

Although increased concentrations of total lecithin in amniotic fluid allow prenatal assessment of fetal lung maturation, it has become clear that routine use of the L/S index may lead to a substantial number of inaccurate predictions. Since disaturated lecithin (DL) is a more specific marker of pulmonary surfactant than total lecithin, we developed a convenient method for measuring this phospholipid in amniotic fluid, and then evaluated its level in pregnant rhesus monkeys of 120 to 163 days of gestation. The method involves osmic acid destruction of unsaturated lipids, chromatographic isolation of disaturated lecithin, and quantitation by phosphorus assay. It can be performed in approximately 5 hours on 4 ml. of amniotic fluid and yield 67 +/- 3 per cent average recovery of added 14C-dipalmitolyl lecithin. The results of analyzing 36 rhesus amniotic fluid specimens showed the disaturated lecithin and the disaturated lecithin/sphingomyelin ratio (DL/S) increase sharply after 150 days of gestation, consistent with the pattern of lung maturation in this species. We conclude that disaturated lecithin can be readily quantitated in primate amniotic fluid and that its concentration, the DL/S ratio, and percentage of disaturated lecithin are potentially useful indices of fetal lung maturity for the clinical laboratory.

Amniotic Fluid↗
PubMed1983

Exclusion of the fetal brain as the main source of rat and human amniotic fluid oxytocin.

At term relatively high oxytocin concentrations are found in maternal plasma and in rat and human amniotic fluid. To determine the contribution of the fetal brain to these oxytocin levels, the peptide was measured in maternal rat plasma and amniotic fluid 2 days after intrauterine removal of the fetal brains, and in the amniotic fluid of 16 human anencephalics. After removal of the fetal rat brains and in human anencephalic pregnancies normal maternal plasma concentrations and amniotic fluid oxytocin contents were found. Consequently, both maternal plasma oxytocin and amniotic fluid oxytocin are not determined to any substantial degree by the fetal brain.

Amniotic Fluid↗
PubMed2004

[Prenatal diagnosis of common chromosomal aneuploidies on uncultured amniotic fluid cells by fluorescence in situ hybridization].

OBJECTIVE: To evaluate the feasibility of using fluorescence in situ hybridization(FISH) for the detection of a few common chromosome aneuploidies on interphase nuclei of uncultured amniotic fluid cells. METHODS: Amniotic fluid samples were taken from 55 women at 16-32 weeks of pregnancy; interphase FISH was performed for diagnosing Down syndrome and aneuploidies of other four chromosomes 13, 18, X and Y. Then the karyotypes from standard cytogenetic analysis after percutaneous umbilical blood sampling(PUBS) were compared to the FISH results. RESULTS: Each of the 55 uncultured amniotic fluid samples tested with FISH was enumerated 200 nuclei. Fifty-three samples were normal. Two samples were found to have trisomy 21(one is a case of standard trisomy 21 with three signals in all 200 nuclei, the other is a mosaic trisomy 21). CONCLUSION: Interphase FISH analysis of uncultured amniotic fluid cells is a rapid, accurate and very sensitive method. It could be used in the prenatal cytogenetic laboratory.

Adult↗