Maternal diabetes and neonatal respiratory distress. II. Prediction of fetal lung maturity

The use of lamellar body counts to predict fetal lung maturity in pregnancies complicated by diabetes mellitus

OBJECTIVE

The purpose of this study was (1) to correlate amniotic fluid lamellar body counts with the lecithin/sphingomyelin ratio and the presence of phosphatidylglycerol in pregnancies that were complicated by maternal diabetes mellitus and (2) to determine a lamellar body count value that maximizes sensitivity and specificity in the prediction of fetal lung maturity.

STUDY DESIGN

We reviewed our prospectively collected perinatal database from November 1992 through October 1999 to identify pregnancies that were complicated by diabetes mellitus for which fetal lung maturity studies had been performed within 72 hours of delivery. Lamellar body counts were correlated with lecithin-sphingomyelin ratio and phosphatidylglycerol values. The sensitivities and specificities of various lamellar body count cutoff values were calculated with the lecithin/sphingomyelin ratio and phosphatidylglycerol values as indicators of fetal lung maturity. Receiver operating curves were used to determine the lamellar body count that indicated fetal lung maturity. Our neonatal database was reviewed for this same time period to obtain all cases of respiratory distress syndrome. The maternal data were compared with the neonatal data to determine whether distress syndrome had developed in an infant who had undergone fetal lung maturity testing respiratory.

RESULTS

Lamellar body counts were correlated with lecithin/sphingomyelin ratio (r = 0.51, P <.001) and phosphatidylglycerol values (r = 0.57, P <.001) in 90 diabetic pregnant patients. A lamellar body count of 37,000/microL was found to have a sensitivity of 80% and a specificity of 100% in the prediction of fetal lung maturity by standardized methods of phospholipid analysis. There were no cases of neonatal respiratory distress syndrome in this study population.

CONCLUSION

The lamellar body count is a valid, rapid screening test for the determination of biochemical fetal lung maturity in pregnancies that are complicated by diabetes mellitus. A lamellar body count of > or =37,000/microL correlated with the lecithin/sphingomyelin ratio and phosphatidylglycerol values in the pregnancies of diabetic patients. Use of lamellar body counts in pregnancies that are complicated by diabetes mellitus could decrease the need for time-consuming and more costly phospholipid profiles. A full phospholipid profile is recommended for amniotic fluid specimens with lamellar body count values of <37,000/microL.

Inaccuracy of Ballard scores before 28 weeks' gestation. National Institute of Child Health and Human Development Neonatal Research Network

OBJECTIVE

Ballard scores are commonly used to estimate gestational age (GA). The purpose of this study was to determine the accuracy of the New Ballard Score (NBS) for infants <28 weeks GA by accurate menstrual history and to evaluate NBS as an outcome predictor.

METHODS

Infants weighing 401 to 1500 g in 12 National Institute of Child Health and Human Development Neonatal Research Network centers had NBS performed before age 48 hours. Accuracy of NBS estimates of GA was assessed for infants with GA determined by accurate menstrual history. In a larger cohort of infants, NBS was included in regression models of the association of NBS and death, poor outcome, and duration of hospital stay.

RESULTS

At each week from 22 to 28 weeks GA by accurate menstrual history, NBS estimates exceeded GA by dates by 1.3 to 3.3 weeks, and estimates varied widely (range of widths of 95% CIs for the observations, 6.8 to 11.9 weeks). NBS did not contribute significantly to regression models of death, poor outcome, or duration of hospital stay.

CONCLUSIONS

Inaccuracies in GA determined by the NBS should be considered when treating extremely premature infants, particularly in decisions to forego or administer intensive care. Refinement of GA scoring systems is needed to optimize clinical benefit.

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.

Management of diabetes mellitus in pregnancy

During the past decade, our major objective in the management of pregnancies complicated by diabetes mellitus has become normalization of maternal and, therefore, fetal glucose levels. For most women with insulin-dependent diabetes, this goal may be achieved through the use of multiple insulin injections combined with an appropriate dietary intake. The results of such therapy can now be accurately assessed by means of home glucose monitoring. Patients with gestational diabetes can be properly treated only if they are first identified. Therefore, all pregnant women should be tested for this disorder because screening based on past obstetric history or clinical criteria alone may miss up to 50% of patients with gestational diabetes. Between 1980 and 1984, the perinatal mortality rate reported in the American literature for more than 800 insulin-dependent patients was 21 per 1000, with more than 50% of these deaths resulting from major malformations. Such data emphasize the need to achieve maternal euglycemia before conception, as poor maternal control has been associated with teratogenesis. Prepregnancy assessment should also include a thorough evaluation of maternal vasculopathy.

Maternal diabetes and neonatal respiratory distress. I. Maturation of fetal surfactant

The phospholipid composition of amniotic fluid samples from 30 normal patients and 44 diabetic patients over the last 10 weeks of pregnancy was studied. Higher levels of phosphatidylcholine (PC) and phosphatidylinositol (PI) were found in diabetic pregnancies where there was excellent glucose control. These differences were statistically significant at 34-36 weeks. Phosphatidylglycerol (PG) appeared significantly earlier in the well controlled diabetic pregnancies, but even in the poorly controlled diabetics the levels of PC, PI and PG were comparable to those in normal pregnancies. There was no evidence of delayed appearance of fetal surfactant phospholipids in either the well or poorly controlled diabetic pregnancies. The absolute lecithin (PC)/sphingomyelin (SM) ratio in diabetic pregnancies was generally greater for any given gestational age than those in normal pregnancies. Whilst in most cases this was due to a higher PC concentration, in a few poorly controlled diabetics it was the result of a lower concentration of SM.