Measurement of fetal surfactant production by fluorescence polarization of amniotic fluid in complicated pregnancies

Testing for fetal lung maturation: a biochemical "window" to the developing fetus

Fetal lung maturity testing represents a major milestone in perinatology. This article critically evaluates specific controversies regarding the methodologies used to measure pulmonary surfactant in AF and how well each of these techniques performs both in principle and application. The clinical utility of fetal lung maturity testing as it applies to particularly difficult complications of pregnancy is discussed. These technical and clinical issues are framed by the scientific and empiric evidence that is used as the rationale for such testing and its implementation in the effective management of preterm delivery.

Semiautomated multisample analysis of amniotic fluid lipids by high-performance thin-layer chromatography-reflectance spectrodensitometry

Analysis of the various lipids in amniotic fluid by multisample semiautomated quantitative high-performance thin-layer chromatography (HPTLC) is presented. Amniotic fluid (AF) lipids are extracted by liquid-liquid partition with chloroform-methanol (C-M) (final C-M-AF ratio of 4:2:1, v/v), 4-microliters aliquots of the C-M extract applied by way of an HPTLC autosampler device (Camag) to Whatman HP-K silica gel plates, and the lipids separated in one dimension using chloroform-ethanol-triethylamine-water (30:34:30:8, v/v) and hexane-diethyl ether (50:5, v/v) as the initial and final mobile phases, respectively. The plates were then stained with a 10% solution of copper sulfate in 8% phosphoric acid and placed in an oven with initial and final temperatures of 24 and 120 degrees C, respectively. This HPTLC system allowed resolution of cholesteryl palmitate, triglycerides, free fatty acid fraction, cholesterol, cardiolipin, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, sphingomyelin, and lysophosphatidylcholine. The stained chromatograms were scanned with a Shimadzu CS-9000U spectrodensitometer in the reflectance mode at 310 nm. The lower limit of detection was 20 ng/ml with linear detector response extended to 2 micrograms/ml. Use of this methodology allows the simultaneous analysis of the various lipids in AF for up to 50 samples in ca. 2 h. This method constitutes a sensitive, quantitative, reproducible, and high-capacity system for analysis of AF lipids.

Fetal lung maturity evaluation with fluorescence polarization of the amniotic fluid

Fluorescence polarization of the amniotic fluid from 39 high risk pregnancies requiring preterm delivery was measured in order to assess the maturity of the fetal lung. The study population included 15 cases of intrauterine growth retardation, ten maternal hypertension, five maternal Hodgkin's disease, three placenta previa, two fetal malformation, two polyamnios, one untreated diabetes, one maternal nephropathy. All patients underwent a single amniocentesis before deciding whether to deliver a preterm baby and FP of the amniotic fluid was done within two hours from amniocentesis. In five cases this was > 0.311, the cut-off limit taken as an indicator of fetal pulmonary status, and three of these developed respiratory distress syndrome. In 34 cases FP values were < or = 0.311; in spite of the apparent lung maturity two of these newborns developed respiratory distress syndrome. On the basis of these results the FP sensitivity was calculated as 60%, specificity 94% and the overall accuracy 90%.

Is indicated or spontaneous preterm delivery more advantageous for the fetus?

We performed a case-control study to determine whether fetuses delivered prematurely because of pregnancy complications (primarily pregnancy-associated hypertensive disease) had a different neonatal course than that of those born after either spontaneous preterm labor or after premature rupture of the membranes. Two case-control populations were matched by gestational age at delivery, fetal sex, and race. There was no perinatal survival advantage in babies delivered from "stressed" pregnancies. Selected neonatal morbidities were generally similar, but there was an increased incidence of necrotizing enterocolitis in babies born after preterm labor and a higher incidence of both necrotizing enterocolitis and neonatal sepsis after premature rupture of the membranes. We conclude that a "stressed" pregnancy confers a negligible survival advantage to the fetus.

Fluorescence polarization changes with gestational age in amniotic fluid of rabbit and guinea pig

The variation of amniotic fluid microviscosity with gestational age was measured in rat, rabbit, and guinea pig. In rat, the changes followed the same pattern as known for women, microviscosity being high during early and mid-gestation and markedly lowering 12 h before delivery. Surprisingly, an opposite trend was observed in rabbit and guinea pig amniotic fluid. Moreover, the lecithin to sphingomyelin ratio markedly rose in late gestation in all species considered. Qualitative and quantitative analysis of lipids and phospholipids were performed in woman and rabbit amniotic fluids at early and late gestational ages. Among all the parameters measured, the most important differences that can influence the amniotic fluid microviscosity are the presence of very high levels of lysophosphatidylcholine both in early and late gestation in rabbit (much higher than in woman) and the cholesterol to total phospholipid ratio which decreased with gestational age in woman but remained stable in rabbit. The Arrhenius plot of the logarithm of microviscosity against the reciprocal of absolute temperature of mature and immature amniotic fluids from woman and rabbit was also determined. The temperature profiles confirmed the differences in lipid profile between woman and rabbit in early and late gestation which could be quantified on a physicochemical basis by determining the activation energy (delta E) at 25 degrees and 37 degrees C for each curve. This confirmed the opposite patterns in woman and rabbit and showed that amniotic fluid from the immature rabbit was the most fluid.