Amniotic fluid prostaglandins do not reflect human fetal lung maturation

Experimental data suggest the involvement of classic prostaglandins (PG), prostacyclin (PGI2) and thromboxane A2 (TxA2) in fetal pulmonary development. To explore this possibility in man, we assayed serial amniotic fluid samples from 33 women for 13,14-dihydro-15-keto-PGF2 alpha (M-PGF2 alpha, a metabolite of PGF2 alpha), 6-keto-PGF1 alpha (a breakdown product of prostacyclin (PGI2)), and thromboxane B2 (a metabolite of TxA2) as well as for the lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol. No difference in these prostanoids was seen between the samples with the immature (less than 2) or mature (greater than or equal to 2) L/S ratio, or between the samples with undetectable or detectable phosphatidylglycerol. The L/S ratio matured in 16 women and phosphatidylglycerol became detectable in 19 women during serial sampling, but even in these women the changes in the amniotic fluid prostanoids were inconsistent. It is concluded that the amniotic fluid M-PGF2 alpha, 6-keto-PGF1 alpha and TxB2 do not reflect fetal pulmonary maturity.     

Amniotic fluid prolactin and fetal lung maturation

Concentrations of prolactin in amniotic fluid, fetal plasma, and maternal plasma were determined in 34 rhesus monkeys delivered by hysterotomy under general anesthesia at gestational ages of 110 to 160 days (term, 165 days). Included were 15 cases (gestational ages 110 to 143 days) in which the mothers received 2 mg of betamethasone intramuscularly daily for 3 days prior to delivery. Fetal lung maximum volumes were determined in addition to the following indices of fetal lung surfactant: lung alveolar stability, lung phosphatidylcholine concentrations, lung extract surface tensions, and amniotic fluid lecithin to sphingomyelin ratios. Amniotic fluid prolactin was found to correlate significantly with lung alveolar stability (r = 0.51; p less than 0.01), lung phosphatidylcholine (r = 0.51; p less than 0.01), lung extract surface tension (r = -0.39, p less than 0.05) and amniotic fluid lecithin/sphingomyelin ratio (r = 0.50; p less than 0.01). These correlations remained statistically significant even when the effects of gestational age were taken into account. These findings suggest that amniotic fluid may modulate fetal production of surfactant via its prolactin content.     

Amniotic fluid: not just fetal urine anymore.

Amniotic fluid (AF) is a complex substance essential to fetal well-being. This article reviews recent discoveries and the current understanding of the origin and circulation of AF and its nutritive, protective, and diagnostic functions. Future directions for AF research are also discussed.     

Multiple courses of betamethasone to enhance fetal lung maturation do not suppress neonatal adrenal response

Objective: Our purpose was to evaluate the neonatal adrenal gland by provocative testing in neonates of mothers who had received multiple courses of betamethasone to enhance fetal lung maturity. Study Design: Infants of mothers who had received ≥3 courses of betamethasone for fetal lung maturation were enrolled in the study. Twenty-four hours after delivery a baseline serum cortisol concentration was obtained. A synthetic adrenocorticotropic hormone (Cortrosyn) was administered (0.25 mg/1.73 m²). Two hours later a second serum cortisol concentration was obtained. An increase in serum cortisol in response to Cortrosyn was considered a positive test result. Nominal data were compared by means of the Student t test. Results: There were 9 infants enrolled in the study. The mean number of betamethasone treatment cycles was 4.8 ± 1.09. The mean baseline cortisol level was 2.23 ± 0.52 μg/dL, and the mean post–adrenocorticotropic hormone cortisol level was 9.86 ± 1.70 μg/dL. All neonates had a positive adrenocorticotropic hormone test result. Stepwise linear regression showed no association between the number of courses of betamethasone treatment cycles and the post–adrenocorticotropic hormone cortisol concentration. Conclusion: Multiple weekly treatment cycles of betamethasone for fetal lung maturity administered between 24 and 34 weeks’ gestation do not appear to cause adrenal suppression. (Am J Obstet Gynecol 1999;180:1349-53.)     

Amniotic fluid phosphatidylglycerol: an early indicator of fetal lung maturity

Summary. In a study of 766 amniotic fluids, collected from pregnancies between 26 weeks and term, phosphatidylglycerol (PG) was identified in a greater proportion than was a mature lecithin/sphingomyelin (L/S) ratio at all gestational ages between 28 and 38 weeks regardless of the underlying pregnancy complication. The early appearance of PG was particularly striking in amniotic fluids obtained after preterm rupture of membranes.
Since PG has been previously shown to be a useful indicator of the risk of neonatal respiratory distress syndrome, its appearance before a mature L/S ratio suggests that its detection offers a considerable advantage in the management of high-risk obstetric problems in which the earliest possible indication that the fetal lungs are mature is required.     

Amniotic fluid squalene and fetal maturity

Gas chromatographic profiles of neutral lipids in amniotic fluid pellets were analysed for 51 specimens collected from patients in the last two months of pregnancy. The most noticeable change was a large increase in squalene relative to other components in samples at term. By expressing data as a ratio of squalene to cholesterol (S/C), it was possible to accurately predict which amniotic fluid specimens came from patients whose pregnancies were of a gestation of 40 weeks or later. Highest values for S/C and for squalene were obtained for pregnancies which were several weeks overdue.     

Amniotic fluid and fetal tissues are not heated by obstetric ultrasound scanning

Amniotic fluid temperature in first trimester pregnancies and fetal subcutaneous tissue and amniotic fluid temperature in second trimester pregnancies, measured by a thermocouple probe, did not increase during sector, linear-array or Doppler ultrasound scanning. The mean fetal muscle temperature was higher (36.9 degrees C) than mean amniotic fluid temperature (36.6 degrees C) during the second trimester.     

Amniotic fluid lamellar body count: cost-effective screening for fetal lung maturity

OBJECTIVE: To create a highly specific cascade testing scheme for fetal lung maturity using the lamellar body count, lecithin/sphingomyelin ratio (L/S), and phosphatidylglycerol. METHODS: A nondedicated hematology analyzer (Sysmex NE 1500, Toa Medical Electronics, Los Angeles, CA) was used to determine the lamellar body counts of 209 unspun amniotic fluid specimens. Maximally specific lamellar body count cutoffs for biochemical maturity and immaturity were determined using receiver operating characteristic curves. Biochemical lung maturity was defined as either a mature L/S ratio or phosphatidylglycerol. Biochemical lung immaturity was defined as both an immature L/S ratio and an immature phosphatidylglycerol. RESULTS: A lamellar body count of less than 8000 (n = 17) was 100% specific for biochemical lung immaturity (positive predictive value = 100%, negative predictive value = 86%). A lamellar body count of greater than 32,000 was 98% specific for biochemical lung maturity (positive predictive value = 99%, negative predictive value = 63%). CONCLUSION: Testing only specimens where the lamellar body count was greater than 8000 and less than or equal to 32,000 for the L/S ratio and phosphatidylglycerol would preclude the need for 76% of all L/S and phosphatidylglycerol assays. Because the lamellar body count is quick, simple, and universally available, it could serve as an extremely cost-effective screening test for fetal lung maturity.     

Amniotic fluid phosphatidylglycerol and phosphatidylcholine phosphorus as predictors of fetal lung maturity

The contents of phosphatidylglycerol and phosphatidylcholine phosphorus in amniotic fluid (10,000 X g pellets) were studied as predictors of fetal lung maturity. The presence of phosphatidylglycerol predicted the absence of neonatal respiratory distress syndrome with 99% probability. When phosphatidylglycerol was absent, phosphatidylcholine phosphorus was a reliable predictor if measured 3 to 7 days before delivery. The probability that respiratory distress syndrome would not occur was 94% when phosphatidylcholine phosphorus was greater than 6. When measurement was performed within 2 days of delivery, the probability that respiratory distress syndrome would not occur fell to 69%. As measured in amniotic fluid, phosphatidylglycerol and phosphatidylcholine phosphorus are reliable antenatal predictors of fetal pulmonary maturity and, therefore, are useful in the management of a number of obstetric conditions.     

Seminal fluid antisperm antibodies do not reflect those present on the sperm surface

Given the increasing evidence that head-directed antibodies can impair fertilization in vitro, as well as play a role in the impaired entry of sperm into cervical mucus, our findings provide strong support for the direct analysis of immunoglobulins bound to the sperm surface, rather than by indirect analysis through the study of seminal fluid.     

Amniotic fluid collagenase inhibitor: correlation with gestational age and fetal lung maturity

Concentrations of collagenase inhibitor in amniotic fluid correlated with gestational age and with indices of fetal lung maturity such as the lecithin/sphingomyelin ratio and the presence of phosphatidylglycerol. Possible sources of amniotic fluid collagenase inhibitor were sought, and a number of tissues and fluids, both maternal and fetal in origin, were found to contain or synthesize this glycoprotein in significant quantities. The highest concentrations were achieved in cultures of lung fibroblasts implicating the fetal lung as a major source. Although collagenase inhibitor is largely present in a free or available state, its specific role, other than that of a general antiproteinase, has not been determined in amniotic fluid. However, the quantitation of amniotic fluid collagenase inhibitor provides an index of the maturation of the connective tissue of the fetal lung and may reflect the ability of the extracellular matrix to meet neonatal demands.     

Amniotic fluid protease activity, protease inhibitory activity, and fetal lung maturity

Amniotic fluid acid protease and acid protease inhibitory activities were examined in normal pregnancies as a function of gestational age. The acid proteolytic activity of the amniotic fluid is almost constant during gestational weeks 16-29 (26 +/- 13 micrograms globin/ml/2 hrs, mean +/- SD, n = 64). The activity sharply increases after 29 weeks in a time-dependent fashion and reaches a value of 302 +/- 89 (mean +/- SD, n = 13) at 39-40 weeks gestation. Under standard conditions, the ability of amniotic fluid to inhibit bovine pepsin declined during gestation in a linear fashion from 44 +/- 13% (mean +/- SD, n = 36) at 16-18 weeks to 9 +/- 10% (mean +/- SD, n = 41) at 36-40 weeks. A correlation coefficient of r = 0.72 was found between pepsin inhibitory activity and gestational age. No consistent change was noted in the extent of inhibition of the endogenous acid protease throughout pregnancy. In 61 amniotic fluid samples, a correlation coefficient of r = 0.70 was found between acid protease activity and the lecithin/sphingomyelin (L/S) ratio. During the course of this study, five cases of respiratory distress syndrome (RDS) were diagnosed clinically. All five infants had a low protease activity (55 +/- 22 micrograms globin/ml/2 hr, mean +/- SD) as well as a low L/S ratio (0.68 +/- 0.20, mean +/- SD). In contrast, no case of RDS of the newborn was observed among 29 pregnancies with high protease activity and a high L/S ratio. The present observations may suggest a predictive value of amniotic fluid acid protease activity in assessment of fetal lung maturity.     

Amniotic fluid contamination during internal fetal monitoring

The risk of infections associated with intrauterine fetal monitoring was evaluated in 30 consecutive labors. Amniotic fluid samples collected through the intrauterine catheter were found to be contaminated with bacteria in 15 of 30 consecutively monitored patients during labor. Aerobes were the exclusive isolates in eight, anaerobes in five and both in two patients. Eleven patients developed puerperal fever. One patient developed gonococcal amnionitis, and her newborn infant later developed gonococcal septicemia. The equipment--catheters and fetal scalp electrodes--was sterile. The overall risk of infection associated with internal monitoring in our study was 50% for amniotic fluid contamination and 37% for puerperal febrile morbidity.     

Correlation between disaturated phosphatidylcholine in amniotic fluid and fetal lung maturation

The concentrations of disaturated phosphatidylcholine (DSPC), the major component of pulmonary surfactant, were quantified on 528 amniotic fluid samples, which did not show the contamination of blood or meconium and were uncomplicated by polyhydramnios or severe congenital anomalies incompatible with life. 396 samples of amniotic fluid (29 RDS cases) obtained 72 hours before delivery were used to evaluate the reliability of DSPC as a specific indicator in pedicting fetal lung maturation. DSPCs were determined according to the method described by Mason et al. and lecithin/sphingomyelin (L/S) ratios were measured by using two dimensional thin-layer chromatography. The critical points of DSPC and L/S ratio were defined as 1.0mg/dl, 2.0 respectively. The results are as follows. There was a gradual increase in DSPC levels of amniotic fluid with increasing maturity until 35 weeks of gestational age and a rapid rise from 36 weeks to term. About 70% of the amniotic fluids having a significantly higher DSPC level greater than or equal to 5.0mg/dl within 35 weeks of gestation were found to be obtained from pregnant women whose pregnancy was complicated by PROM, threatened premature labor or cervical incompetency and who eventually underwent preterm labor. Out of 58 samples, in which DSPC and the L/S ratio were measured simultaneously, two markers agreed in 47 cases in an immature or a mature value for predicting fetal lung maturation. RDS was correctly predicted in 27 of 60 cases (false negative, 55.0%) with DSPC levels less than 1.0mg/dl. When DSPC levels were 1.0mg/dl or more, there were only two of 336 (0.6%), false positives.(ABSTRACT TRUNCATED AT 250 WORDS)