Amniotic fluid assessment.

The mysterious environment surrounding the fetus for much of his or her life is now being explored with increasing fervor. Assessment of amniotic fluid in the early portion of pregnancy is now possible for fetal karyotype determination. This may permit early diagnosis of abnormal fetuses, increasing the options for patients. As pregnancy progresses, high-resolution ultrasound assessment of amniotic fluid volume is integral to the management of pregnancies at risk for oligohydramnios. Such pregnancies include those who are postdate and those with suspected intrauterine growth retardation. Additional evaluation and ultrasonography are recommended for evaluation of the fetus in this clinical situation. With either hydramnios or oligohydramnios, careful ultrasound assessment of the fetus is essential to rule out significant congenital malformations. Finally, the use of ultrasound-directed amniocentesis in later pregnancy permits an assessment of fetal lung maturity and of the fetus at risk for Rhesus immunization. Attention to detail should increase chances of a successful pregnancy outcome while decreasing neonatal morbidity and mortality.

Total phospholipid choline concentration of amniotic fluid in the assessment of foetal gestational and lung maturity. I. Establishment of a direct enzymic method.

An enzymic assay of the choline-containing phospholipids of amniotic fluid which does not require lipid solvent extraction has been developed. Lecithin and sphingomyelin are the dominant phospholipids in mature lung surfactant. The total phospholipid choline content of amniotic fluid, which represents the molar sum of lecithin and sphingomyelin, may be expected to correlate with foetal lung maturity. The merits of our new analytical method of determination of total phospholipid choline concentration in amniotic fluid are discussed.

Total phospholipid choline concentration of amniotic fluid in the assessment of foetal gestational and lung maturity. II. Correlation study.

Analysis of total phospholipid choline concentration was carried out on amniotic fluid samples obtained from 20 pregnant Nigerian women in established labour to determine the correlation of amniotic fluid phospholipid choline concentration with the gestational ages and maturity of the infants. There was a positive correlation between phospholipid choline concentration and gestational age. All infants whose gestational ages were estimated to be over 36 weeks had a total phospholipid concentration greater than 50 mumols/l. Four infants whose gestational ages were less than 36 weeks had total phospholipid choline concentration less than 30 mumols/l. None of these infants showed any evidence of Respiratory Distress Syndrome.

Assessment of foetal lung maturity.

An important prerequisite for the management of high risk pregnancies is the accurate prediction of foetal lung maturity. A number of indices of foetal lung maturity based on the determination of surfactant constituents in the amniotic fluid have been proposed. Amniotic fluid contains phospholipids, including phosphatidylcholine (lecithin), sphingomyelin, phosphatidylinositol and phosphatidylglyerol (PG), some enzymes of the pathways of phospholipid synthesis, lamellar bodies, and lung specific apoproteins. The amount of these substances in amniotic fluid changes towards the end of gestation in a manner related to foetal lung maturity. Determination of the lecithin to sphingomyelin (L/S) ratio is by far the most widely used and accepted method. However, there is still controversy regarding the high incidence of false immature values, and the increased incidence of false mature values (from 1 to 15%) especially in pregnancies complicated by diabetes mellitus; an immature L/S ratio may predict respiratory distress syndrome (RDS) only in about 50% of cases. The incidence of false immature L/S ratio as well as other amniotic fluid tests depends upon patient variability, method employed, threshold taken for differentiating a normal from an abnormal condition, and on the fact that only few authors report their results in terms of sensitivity and specificity. Where laboratory facilities are minimal, it is advisable to perform the shake test or to measure the optical density of amniotic fluid. However, when these tests indicate immaturity, additional tests, such as determination of the L/S ratio or the lung profile (including PG), must be performed. The utilization of these tests is recommended for: 1) timing of delivery prior to elective caesarean section; 2) management of complicated pregnancies; and 3) recognizing indications for pharmacologic prevention of RDS in utero or at delivery.

Current perspectives in assessment of fetal pulmonary surfactant status with amniotic fluid.

In recent years, improvements in analytical methodology and clinical management of maternal-fetal diseases have altered the understanding of data from amniotic fluid analysis. Delays in phospholipid production or lung function are not currently reported in maternal diabetes. Fetal lung function following glucocorticoid therapy or premature membrane rupture is uncoupled from amniotic fluid phospholipid concentrations, which do not have the usual significance in these circumstances. Phosphatidylglycerol (PG) is present prior to the usual time it is detected by thin layer chromatography (TLC) methods, which vary in sensitivity for PG. Consequently, the significance of its "absence" is highly varied. These observations are discussed in light of the earlier methods and data, along with new perceptions of the functions of the individual phospholipids and apoproteins, the regulatory mechanism of surfactant production, and the relationship of amniotic fluid components to neonatal lung function.

Fetal assessment based on fetal biophysical profile scoring: experience in 19,221 referred high-risk pregnancies. II. An analysis of false-negative fetal deaths.

The incidence of false-negative fetal death, which is defined as stillbirth unrelated to major anomaly or alloimmunization occurring after a last normal fetal biophysical score, was determined in 19,221 referred high-risk pregnancies. The calculated rate of fetal death after a last normal test was 0.726/1000 (14 deaths), which remained relatively constant despite a progressive increase in tests and patients studied. We conclude that a normal fetal biophysical profile score confers a high probability of perinatal survival.

A calibrated fluorescence polarization assay for assessment of fetal lung maturity.

The mechanism of a new fluorescence polarization method for measuring phospholipid in amniotic fluid is described. The fluorescence polarization of a surfactant fluorescent dye solubilized in amniotic fluid correlates significantly with the L/S ratio. Model studies indicate that this results primarily from partitioning of the dye between endogenous albumin, which causes a high fluorescence polarization, and dispersed phospholipid, which causes a much lower polarization. The fluorescence polarization can be compared with a calibration curve to give the ratio of phospholipid to albumin in the sample. This procedure may prove useful in antenatal assessment of fetal lung maturity.

A comparison of HPLC and TLC in the assessment of amniotic fluid lecithin/sphingomyelin ratio.

One hundred amniotic fluid (AF) specimens of women at 28 to 37 weeks gestation were obtained during labor for lecithin/sphingomyelin ratio (L/S ratio) study by using high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The results are divided into two groups: one with L/S ratio at or more than 2, and the other with L/S ratio of less than 2. Of the 80 measured by HPLC with the ratio of above 2 or 1.3%, one suffered respiratory distress syndrome (RDS); of the 65 measured by TLC also with the ratio of above 2 or 3.1%, two developed RDS. The result bears no great significance here. However, in the groups with L/S ratio of less than two, the results were very significant: 17 of 20 estimated by HPLC happened to have RDS for an incidence of false positive rate of 15% compared with a 54.3% in 16 of the 35 women evaluated by TLC.

The ethical dimensions of policy for prenatal diagnostic technologies: the case of maternal serum alpha-fetoprotein screening.

New technologies have dramatically increased the number of fetal abnormalities that can be detected and, in some cases, effectively treated during the prenatal period. Considering the potential health benefits to children and parents from early detection of fetal abnormalities, various forms of mandatory prenatal screening programs have been suggested. In order to explicate the ethical dimensions of mandatory screening in general and to demonstrate the role of nurses in prenatal screening programs, maternal serum alpha-fetoprotein screening is analyzed. The benefits, risks, and potential consequences from the broad use of this technology are discussed in conjunction with the rights of fetuses and pregnant women. An active role in the formation of health policy that might regulate new technologies affecting maternal-fetal-newborn health is suggested as a fundamental responsibility of the nursing profession.

Protein analysis in amniotic fluid and fetal urine for the assessment of fetal renal function and dysfunction.

Micromolecular proteins (molecular weight less than 68 kD) in amniotic fluid are assumed to be derived largely from fetal urinary excretion and therefore may reflect fetal kidney function and maturation. Microprotein concentrations in amniotic fluid, neonatal urine and urine of fetuses with bilateral urinary tract dilation were analyzed using microgradient gel electrophoresis to separate proteins according to their molecular size. Alpha-1-microglobulin and beta 2-microglobulin were assayed as singular micromolecular marker proteins. Microproteins in amniotic fluid decreased progressively with advancing gestation during the 3rd trimester. Micromolecular protein concentrations in the first postnatal urine of healthy infants born prematurely or at term were similar to those in amniotic fluid of corresponding fetal age and yielded an identical developmental pattern. A strong correlation existed between the microprotein concentrations in amniotic fluid and fetal urine. It is concluded that fetal urinary production is the main determinant for the microprotein content of amniotic fluid and that a major fetal pathway exists for the intrauterine metabolism of these proteins. The 3rd trimester decrease in amniotic fluid seems to be dependent on the increasing reabsorption capacity of proximal tubular cells representing morphological and functional kidney maturation. The exact diagnostic value of microprotein analysis for the assessment of disturbed fetal kidney function has still to be defined by further investigation.

Utilidad de la valoración de la edad gestacional por parámetros del líquido amniótico (células naranja y densidad óptica) / Utility of valuation of the gestational age for amniotic fluid parameter (orange cells and optic density)

Se trata de un estudio prospectivo dende se incluyeron 255 pacientes, atendidas en el Servicio de Perinatología del Hospital "Dr. Adolfo Prince Lara", de Puerto Cabello, entre noviembre de 1980 a octubre de 1986, que precisaban la fecha de última regla o determinadas por ecografía, corroborándose a través de la evaluación neonatal por el método de Capurro; a dichas pacientes se les practicó 291 amniocentesis bajo control ecográfico, determinándose el a 450 nm y porcentaje de células naranja utilizando estos resultados para calcular la edad gestacional de acuerdo a fórmulas y tablas realizadas por Belitzky. Se calcularon las diferencias de estimación y los errores porcentuales para cada grupo de edad y se correlacionaron estadísticamente. Se concluye que el método estudiado es útil para estimar la edad gestacional, teniendo un error porcentual de ñ 3%

The assessment of foetal lung maturity by chemical analysis of amniotic fluid.

Advances in the understanding of the neonatal respiratory distress syndrome have led to a proliferation of amniotic fluid tests. Measurement of pulmonary surfactant production is the most direct means of assessing pulmonary maturity. Assays of surfactant are subjected to certain pre-analysis sources of variation, such as variability in amniotic fluid volume, sample collection site, centrifugation speed and time, and contamination with blood and/or meconium. Amniotic fluid surfactant assays can be divided into biochemical and functional tests. When properly performed, both approaches yield results that correlate well with clinical findings. However, no single method has achieved the distinction of total reliability and universal applicability. In most tests the value for mature lungs is almost 99% accurate. On the other hand, immature values have very low accuracy. Therefore, it is advisable to perform an additional test or to repeat the determination. The determination of the lecithin/sphingomyelin ratio is characterized by sufficient accuracy for routine analyses. For scientific studies we recommend the use of a capillary gas-chromatographic method allowing an accurate assessment of dipalmitoylphosphatidylcholine, the most important surfactant constituent.

Clinical and economic considerations associated with testing for fetal lung maturity.

Performing multiple tests of fetal lung maturity on amniotic fluid samples may not use the individual test results and laboratory personnel most effectively. To determine the best strategy for fetal lung maturity testing, we analyzed our experience with use of a variety of procedures. Clinical usefulness was assessed according to sensitivity, specificity, predictive values, and efficiency. Economic and technical aspects analyzed included time and personnel requirements, availability of tests, and expense of each procedure. Several testing sequence approaches were compared for efficiency and cost. In our laboratory the foam stability index proved to be the most useful initial test of fetal lung maturity, reserving more expensive and time-consuming tests for instances in which the foam stability index is immature. Routine multiple testing did not enhance clinical usefulness and greatly increased costs. Development of a testing strategy using a rapid, inexpensive, and widely available test such as the foam stability index would promote clinical and economic efficiency.

Fetal maturity cascade: a rapid and cost-effective method for fetal lung maturity testing.

One hundred ninety-three amniotic fluid samples were tested for fetal lung maturity using a maturity cascade scheme involving the sequential use of, in order, the shake test, fluorescence polarimetry, and lecithin: sphingomyelin (L:S) ratio. If any of these tests indicated maturity, the sequence was terminated and no further test was performed, and the fetus was considered mature. Seventy percent of the tests yielded mature values and of these, 85 (63%) required a shake test only, 37 (27%) had a shake test and a fluorescence polarimetry, and only 14 (10%) required all three tests. From these 193 amniocenteses, 111 patients delivered within 72 hours of the procedure. One of 94 infants had respiratory distress syndrome after a mature test (1% false maturity) and ten of 17 had respiratory distress syndrome after an immature cascade (41% falsely immature). This approach saves time and cost and by confirming immaturity with multiple tests only when necessary and may improve predictability of neonatal respiratory distress syndrome.

Assessment of the AmnioStat-FLM immunoagglutination test for phosphatidylglycerol in amniotic fluid.

One hundred and eight amniotic fluids were assayed by the AmnioStat-FLM (A-FLM) immunological agglutination test for phosphatidylglycerol (PG) and simultaneously measured enzymatically for PG content. Of 52 amniotic fluids found to be PG negative by the A-FLM method, all had enzymatic PG concentrations less than or equal to 1.5 mumol/l. Conversely, of 56 amniotic fluids judged to be either PG positive or weak positive, all but five had enzymatic PG concentrations greater than 1.5 mumol/l. The sensitivity of the A-FLM assay employed clinically for predicting foetal lung maturity was 89% and the specificity was 100%. The overall predictive accuracy of the test could be improved by providing controls at lower, more appropriate PG concentrations. Ninety-one fluids analysed by the A-FLM kit were subsequently tested for the presence of PG by two-dimensional thin-layer chromatography (2D TLC). A 94%-concordance between the methods was found.

Fetal assessment by biophysical profile scoring: 1985 update.

In extrauterine medicine, physicians have come to rely upon sampling of multiple biophysical variables as a means of differentiating states of well-being and compromise. This basic tenet of medicine is expressed by obtaining an Apgar score or some variant in the newborn and as a measure of vital signs in later life. Few, if any, decisions regarding well-being are ever based on a single-variable assessment and, conversely, definition of compromise is rarely based upon a single variable. Through the use of dynamic ultrasound imaging it now becomes possible to visualize the fetus and its biophysical responses in health and disease. Through such visualization it becomes possible to bring to bear some of the basic principles that sustain extrauterine medicine on the intrauterine patient, the fetus. Fetal biophysical profile scoring describes a method that encompasses this concept. The results obtained by application of this method are promising. We would argue that consideration of multiple fetal biophysical variables will, in most instances, yield superior results to single-variable monitoring alone. Hence we have abandoned antepartum fetal heart rate testing as the sole method of fetal risk assessment and used the tool only in conjunction with others of the many variables that may be monitored by dynamic ultrasound methods. This concept of multiple-variable analysis as the superior method for fetal assessment seems clear and well-justified. It is our opinion, however, that the concept of fetal bioprofile scoring may be more important than the method itself in its original description.(ABSTRACT TRUNCATED AT 250 WORDS)