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High-speed centrifugation of amniotic fluid enables separation of surfactant-containing lamellar bodies. Fifty-three amniotic fluid samples from pregnancies of 28 to 39 weeks' gestation were examined for fetal lung maturity by measuring fluorescence polarization (P). For each sample the P value was determined at 37C on both the whole amniotic fluid and on the surfactant-containing lamellar bodies obtained by centrifugation at 10,000 X g. A close linear correlation (r = 0.80) was found between the P value of the amniotic fluid samples and that of the lamellar bodies. There was no difference in the specificity for discrimination of hyaline membrane disease cases by both methods (93.5%) with 95% confidence limits of 82.1 to 98.6%. Because high-speed centrifugation enables the selective sedimentation of pulmonary surfactant, determination of the lamellar body P value may offer a practical solution for the estimation of fetal lung maturity in amniotic fluid samples contaminated with blood.

406 midtrimester amniotic fluid samples were examined for alpha-fetoprotein (AFP) levels and fetal karyotyping. 44 cases with Down syndrome, 12 with Klinefelter syndrome and 14 with other chromosomal abnormalities were diagnosed. The AFP levels were below the median value for the normal pregnancies in 38 of the 44 Down syndrome-affected fetuses. The mean AFP value was significantly lower (p less than 0.0001) in this group. No such difference was found for fetuses affected by Klinefelter syndrome or other chromosomal aberrations. Almost all of the values for the Down syndrome-affected fetuses were, however, within the normal range, thereby precluding the possibility of using this measurement as an alternative to fetal karyotyping as a screening test for Down syndrome.

One of the most convenient ways to determine fetal lung maturity is by measuring the fluorescence polarization (P) of the amniotic fluid at room temperature. With sensitivity fixed on 100%, specificity is relatively unsatisfactory. The present study compared the predictive power of fluorescence polarization measured at temperatures 25C (P25), 37C (P37), and 40C (P40) among 195 consecutive samples tested at both 25C and 37C, with a subgroup of 86 samples tested also at 40C. A better separation between the results for fetuses with and without hyaline membrane disease is attained at P37, demonstrated by a greater mean standardized distance (distance between P values for those patients with and the mean P value for those patients without hyaline membrane disease in unit of standard deviation of the latter; 1.597 +/- 0.528 for P25 versus 2.332 +/- 0.591 for P37). Fixing the sensitivity at 100%, the specificity of P25 and P37, were 68.9 and 94.9%, respectively; a highly significant difference (P less than .001). The specificity of P40 was 90.5%, lower than that of P37. P37 is the best predictor and adding either P25 or P40 does not improve the prediction of lung maturity. It is concluded that P37 should replace P25 as the definite index for fetal lung maturity.

Determination of fetal lung maturity by measurement of the fluorescence polarization (P) value of the amniotic fluid at room temperature has become the method of choice in an increasing number of perinatal units because of its simplicity and relatively high predictive value. Nevertheless, its power to discriminate between cases with and without hyaline membrane disease (HMD) needs improvement. To this end, we assessed the discriminative power of the P value at the physiological temperature of 37 degrees C (P37) as compared with the power at 25 degrees C (P25). The study group consisted of 288 consecutive cases at risk for preterm delivery. Samples from all 288 cases were measured at 25 degrees C and samples from 112 of these were measured concurrently at 37 degrees C as well. HMD occurred in 27 infants of the total group, nine of whom belonged to the subgroup tested at both temperatures. When sensitivity was fixed at 100% the specificity of P37 was 97% as compared to 79% for P25 (p less than 0.001). The percentage of cases with infants free of HMD who had borderline P values was also significantly smaller: 1% vs 21%, respectively (p less than 0.001). Although data on more HMD cases are needed to establish the precise threshold of lung maturity for P37, we conclude that P37 is a considerably better discriminator for fetal lung maturity determination than P25.

The fluorescence polarization of amniotic fluid, a measure of fetal lung maturity, was determined in 518 amniotic fluid samples obtained by amniocentesis. The subjects were divided into seven clinical groups: premature contractions, premature rupture of the membranes, pregnancy-induced hypertension, diabetes, intrauterine growth retardation, vaginal bleeding, and "other" for gestational-age groups of 30 weeks or less, 31-36 weeks, and 37 or more weeks. The proportion of mature values (fluorescence polarization 0.285 or lower) increased progressively from 12.5% at 27-28 weeks to 100% at 39-40 weeks. In the 31-36-week gestation group, the proportion of mature values in subjects with premature rupture of the membranes (84.6%) was significantly higher than in those with premature contractions (60%), severe pregnancy-induced hypertension (50%), mild pregnancy-induced hypertension (55.2%), diabetes class A (50%), insulin-dependent diabetes (60%), and other (63.5%). The mean +/- SD fluorescence polarization value was significantly lower in premature rupture of the membranes (0.256 +/- 0.030) than in premature contractions (0.274 +/- 0.032), mild and severe pregnancy-induced hypertension (0.280 +/- 0.027 and 0.280 +/- 0.035, respectively), and class A and insulin-dependent diabetes (0.285 +/- 0.018 and 0.277 +/- 0.030, respectively). The severity of pregnancy-induced hypertension and diabetes did not appear to influence either the fluorescence polarization value or the proportion of mature results. With the exception of a marked influence of premature rupture of the membranes, abnormal pregnancy conditions did not appear to have a significant effect on fluorescence polarization of amniotic fluid.

Estimation of fetal lung maturity by examination of amniotic fluid samples is unreliable in the presence of blood. Centrifugation of amniotic fluid at 10,000 X g separates the surfactant-containing lamellar bodies from contaminants, such as serum lipids. The influence of serum contamination of amniotic fluid was evaluated using the fluorescence polarization technique for determination of fetal lung maturity. Addition of serum changed the amniotic fluid P value of both the amniotic fluid and the lamellar body pellets in the direction of the P value of serum. After centrifugation at 10,000 X g, there was no significant difference in the P value of the pre- and postcontamination samples, demonstrating that centrifugation resulted in the removal of pulmonary nonrelevant lipids in contaminated amniotic fluid specimens. In 24 patients in whom the amniotic fluid sample was blood stained, the P value on the lamellar body pellet compared favorably to that obtained from noncontaminated samples.