Neonatal morbidity occurs despite pulmonary maturity prior to 39 weeks gestation

OBJECTIVE

To compare outcomes among late-preterm or early-term neonates according to fetal lung maturity (FLM) status.

STUDY DESIGN

We conducted a retrospective cohort study of 234 eligible singletons delivered after FLM testing before 39 weeks gestation at our center over a 2-year time period. A primary composite neonatal outcome included death and major morbidities.

RESULT

The overall rate of primary composite morbidity was 25/46 (52.2%) and 61/188 (32.4%) in the immature/transitional and mature groups, respectively. After adjustment for confounders including gestational age, the composite outcome was not significantly different; adjusted odds ratio (aOR)=1.4 (confidence interval (CI)=0.7-3.0). The rate of respiratory distress syndrome was significantly higher in the immature/transitional group; odds ratio=3.4 (CI=1.1-10.3) as expected.

CONCLUSION

FLM status did not correlate with the spectrum of neonatal morbidities in late-preterm and early-term births. Neonatal complications remained common in both groups.

The effect of common clinical contaminants on amniotic fluid fluorescence polarization results

OBJECTIVE

To determine the effect of blood, meconium, and vaginal secretions on amniotic fluid (AF) fluorescence polarization results.

METHODS

Amniotic fluid was collected by transabdominal amniocentesis from women at 20-41 weeks of gestation and contaminated with blood, meconium, and vaginal secretions to concentrations of 0.5, 1, 2, 5, and 10%. An additional 20% concentration was performed with meconium and vaginal secretions. Fluorescence polarization was determined by a TDx Analyzer with the NBD-PC fluorescent probe. Results were compared for each contaminant by concentration level using repeated-measures analysis of variance.

RESULTS

Forty-eight samples from women at a mean gestational age of 35 weeks (range 20-41.5 weeks) were evaluated. Before contamination, 16 (33%) samples had fluorescence polarization values greater than 290 mPol (immature), 10 (21%) were 260- 289 mPol (transitional), and 22 (46%) were less than 260 mPol (mature). Contamination with blood significantly altered fluorescence polarization values in AF samples with baseline values in the immature and mature categories such that values trended toward the transitional range. Contamination of baseline immature samples with vaginal secretions at 20% contamination level resulted in more mature fluorescence polarization values. Contamination with meconium more than 2% in the baseline immature category or more than 20% in the baseline transitional category also resulted in significantly more mature fluorescence polarization values.

CONCLUSION

Amniotic fluid contamination with blood can result in more transitional range fluorescence polarization values, whereas contamination with meconium and vaginal secretions can result in more mature fluorescence polarization values.

Standards of laboratory practice: evaluation of fetal lung maturity

In this standard of laboratory practice I recommend guidelines for fetal lung maturity (FLM) testing. If possible, obtain a 10-mL uncontaminated sample by amniocentesis. Keep the amniotic fluid at 4 °C and mix well before testing. If centrifugation is required, strictly adhere to the protocol. Most laboratories should offer a rapid test, such as fluorescence polarization, phosphatidylglycerol, or foam stability index, daily on both a routine and emergency basis. Requests for lecithin/sphingomyelin ratio may be referred to a reference laboratory. Communicate immediately the results of any FLM test to the ordering location. The report should contain the result, sample contamination, and reference information. Separate reference intervals for diabetic patients are not recommended.

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.