Assessment of fetal lung maturity: relationship of gestational age and pregnancy complications to phosphatidylglycerol levels

Towards quantifying biomarkers for respiratory distress in preterm infants: Machine learning on mid infrared spectroscopy of lipid mixtures

Neonatal respiratory distress syndrome (nRDS) is a challenging condition to diagnose which can lead to delays in receiving appropriate treatment. Mid infrared (IR) spectroscopy is capable of measuring the concentrations of two diagnostic nRDS biomarkers, lecithin (L) and sphingomyelin (S) with the potential for point of care (POC) diagnosis and monitoring. The effects of varying other lipid species present in lung surfactant on the mid IR spectra used to train machine learning models are explored. This study presents a lung lipid model of five lipids present in lung surfactant and varies each in a systematic approach to evaluate the ability of machine learning models to predict the lipid concentrations, the L/S ratio and to quantify the uncertainty in the predictions using the jackknife + -after-bootstrap and variant bootstrap methods. We establish the L/S ratio can be determined with an uncertainty of approximately ±0.3 mol/mol and we further identify the 5 most prominent wavenumbers associated with each machine learning model.

The role of VEGF and its soluble receptor VEGFR-1 in preterm newborns of preeclamptic mothers with RDS

OBJECTIVE

We measured vascular endothelial growth factor (VEGF) and soluble VEGF receptor 1(sVEGFR-1) concentrations in cord blood and tracheal aspirate fluid (TAF) in order to investigate the role of them in lung maturation and the severity of respiratory distress syndrome (RDS) in preterm newborns, born to preeclamptic mothers.

METHODS

Newborns were divided into two groups as preterms born to preeclamptic mothers and preterms born to healthy mothers. They were also divided into two groups as severe RDS (sRDS) and mild RDS (mRDS) according to the need of surfactant and extent or type of ventilatory support. The concentrations of VEGF and sVEGFR-1 in cord blood and TAF (only in preterms with sRDS) were assayed by standardized enzyme-linked immunosorbent assay.

RESULTS

When the patients were evaluated as sRDS and mRDS, cord blood VEGF and VEGF/sVEGFR-1 concentrations of preterms with sRDS were significantly lower than the concentrations of preterms with mRDS. Conversely, cord blood sVEGFR-1 concentrations of preterms with sRDS were significantly higher than the concentrations of preterms with mRDS. VEGF and sVEGFR-1 concentrations in TAF could be compared only between sRDS preterms, born to preeclampsia (+) and (-) mothers. No statistical significance was detected between the two groups when sVEGFR-1, VEGF and VEGF/sVEGFR-1 concentrations in TAF were compared.

CONCLUSION

Preeclampsia seems not to have an important effect on VEGF and sVEGFR-1 concentrations of preterm newborns both in cord blood and in TAF. Low VEGF and high sVEGFR-1 concentrations seem to be associated with the severity of RDS irrespective of preeclampsia, suggesting that VEGF may be one of the main components of lung maturation.

[Preeclampsia increases the risk of hyaline membrane disease in premature infant: a retrospective controlled study]

OBJECTIVES

Relation between preeclampsia (PE) and hyaline membrane disease (HMD) is still controversial. We found interesting to contribute to the study of this relation by comparing a HMD group to a control group with the aim to know if the risk to develop HMD was more important in case of PE.

MATERIAL AND METHODS

Two groups of premature infants (HMD group and control group) weighing less than 2000g and hospitalized between 1st January 2004 and 31st December 2005, were compared for data concerning mother (age, parity, diabetes, corticotherapy), PE (severity, complications, type and treatment), delivery (mode, infectious context, perinatal asphyxia) and neonatal stay (gestational age, birth, weight, sex). A multivariate analysis by logistic regression was used to control the effect of potential confounding variables that were considered risk factors for HMD.

RESULTS

Ninety-seven neonates were retained and were compared to 97 control. PE was present in 71 cases in HMD group and in 51 cases of control group. This difference was statistically very significant (p=0.003). When we controlled for confounding variables, there was a significant increase in risk to develop HMD (odds ratio, 1.3; 95% confidence interval, 0.7-1.8).

CONCLUSION

The risk to develop HMD, in premature infant weighing less than 2000g, is increased in case of PE. These finding support that fetal lung maturity is not accelerated in PE, in the opposite, it is delayed.

The association between hyaline membrane disease and preeclampsia

OBJECTIVE

The purpose of this study was to determine whether hyaline membrane disease is increased in newborn infants who are born to women with preeclampsia compared with control subjects.

STUDY DESIGN

This was a historic cohort study of deliveries between 24 and 37 weeks of gestation at the Medical University of South Carolina from 1996 through 2002. Singleton infants who were born to women with preeclampsia were compared with nonpreeclamptic control subjects. The incidence of hyaline membrane disease was compared by chi 2 analysis and Fisher exact test, with significance at a probability value of <.05. Logistic regression analysis was performed to address potential confounders.

RESULTS

There were 814 women with preeclampsia and 3021 control subjects. When we controlled for confounding factors, there was a significant increase in the incidence of hyaline membrane disease in the preeclamptic group overall (odds ratio, 1.35; 95% CI, 1.03-1.78). The risk was more pronounced in neonates who were born at 32 weeks of gestation (odds ratio, 1.93; 95% CI, 1.28-2.91).

CONCLUSION

The risk of hyaline membrane disease in neonates at < 32 weeks of gestation is increased in patients with preeclampsia. This supports the contention that fetal lung maturity is not accelerated in preeclampsia.

Fetal adaptation to stress. Part I: acceleration of fetal maturation and earlier birth triggered by placental insufficiency in humans

This review is an attempt to provide an integrative view for the biological changes triggered by fetal stress through a multidisciplinary approach. Acceleration of brain and lung maturation in certain risk pregnancies was first described clinically and confirmed by biochemical, electrophysiological and experimental data. Moreover, new experimental findings suggest that a fetal clock centrally mediated by fetal nutritional status could determine timing of parturition. However, some skepticism persisted about the usefulness of this body of knowledge for obstetrical management in developed countries. The interest concerning this adaptation to intrauterine stress was later renewed from various sources, as developed in Part II.

Prospective delivery of reliably dated term infants of diabetic mothers without determination of fetal lung maturity: comparison to historical control

OBJECTIVE

To determine whether omitting fetal lung maturity (FLM) testing prior to delivery in term pregnancies complicated by gestational (GDM) and pregestational diabetes mellitus would increase the risk of neonatal respiratory distress syndrome (RDS).

METHODS

In a 2-year study (1990-91), 1,457 pregnant women with accurately dated pregnancies were enrolled after 37 completed weeks and prospectively followed through delivery without FLM testing (study group). The prevalence of RDS and other neonatal outcomes was compared with a historical control group (n = 713, 1988-89) who had undergone determination of lecithin/sphingomyclin ratio prior to delivery at term. Logistic regression analysis was performed to determine independent predictors of RDS.

RESULTS

The study group compared to the control group had less severe diabetes: diet-controlled GDM, 35% vs. 18%, respectively; insulin-requiring GDM, 42% vs. 42%, respectively; undiagnosed type-2 diabetes, 14% vs. 31%, respectively; and pre-existing diabetes, 9.6% vs. 8.8%, respectively, p < 0.001. RDS rates in the study group (0.8%) and control group (1.0%) were not significantly different, nor were rates of resuscitation at delivery, neonatal intensive care admission or hospitalization days. Logistic regression analysis found only Cesarean delivery to be independently predictive (adjusted OR 2.21, 95% CI 2.04-2.27) of RDS. Non-predictive variables included FLM testing, diabetic classification, insulin use, poor third-trimester glycemic control, chronic hypertension, pre-eclampsia, labor, neonatal gender, gestational age or large-for-gestational-age fetuses.

CONCLUSIONS

Routine FLM testing did not change the RDS prevalence in reliably dated, term infants of diabetic mothers and should be abandoned. Delivery by Cesarean section was associated with increased RDS.

The controversy surrounding fetal lung maturity in diabetes in pregnancy: a re-evaluation

It is beyond the scope of this article to discuss the biochemical markers of fetal lung maturity and their pathophysiological characteristics. This information can be found in several textbooks and review articles. Instead, this article addresses controversial issues that confront the obstetrician in daily clinical practice related to the role of diabetes (glucose) as the teratogen for lung morbidity, and the association between lung maturity testing results and actual lung morbidity.

Influence of metabolic control of pregnant diabetics on fetal lung maturity

We studied the relationship between the metabolic control of pregnant diabetics and fetal lung maturity. In 31 diabetic and 20 normal pregnancies we analysed phospholipids in amniotic fluid and glycaemic control parameters. There were no differences in amniotic fluid lecithin/sphingomyelin (L/S) and phosphatidylinositol/sphingomyelin (PI/S) ratios between pregnant diabetics with strict metabolic control and the control group. Pregnant diabetics with poor metabolic control had significantly different L/S and PI/S ratios than the normal pregnant women. Six women in this group of poorly controlled diabetics had mature surfactant in amniotic fluid (L/S > or = 2.7 and presence of phosphatidylglycerol) at 32-34 weeks of amenorrhea; the difference was significant (p < 0.05) with respect to the control group. These six women had recurrent hypoglycaemic episodes (6.4 +/- 1.3 episodes/week) at 14-27 weeks of amenorrhea. Our findings suggest that hypoglycaemic stress on the fetus could disturb fetal synthesis of pulmonary phospholipids.

Amniotic fluid phospholipid analysis in the fetus with congenital diaphragmatic hernia

The substantial morbidity and mortality of congenital diaphragmatic hernia (CDH) is attributed to the pulmonary hypoplasia caused by the presence of abdominal viscera in the chest during intrauterine life. Recent experimental studies suggest that surfactant deficiency may also contribute to CDH pathophysiology. Clinically, the amniocentesis-derived lecithin to sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) data are used to assess fetal lung maturity. We have performed amniotic fluid phospholipid analyses at 33 to 38 weeks' gestation in 18 fetuses with prenatally diagnosed CDH to assess fetal lung maturity, plan optimal timing for delivery, and selectively employ prenatal glucocorticoid or postnatal surfactant therapy. Compared with published control values from uncomplicated pregnancies, there was no difference in the L/S ratio or PG in the CDH fetus. Based on amniotic fluid phospholipid data, the human CDH fetus is not surfactant-deficient.

Corticotrophin releasing hormone levels in human plasma and amniotic fluid during gestation

OBJECTIVE

Corticotrophin releasing hormone, a hypothalamic neuropeptide also made in placenta, may regulate fetal maturation in a stress-responsive manner. The objectives of this study were: (1) to determine if levels of corticotrophin releasing hormone in the amniotic fluid correlate with fetal lung maturation; (2) to confirm that third trimester plasma levels of corticotrophin releasing hormone are increased in patients with pregnancy-induced hypertension compared to normotensives, and (3) to increase the recovery of extracted corticotrophin releasing hormone from plasma and amniotic fluid.

DESIGN

(1) Levels of corticotrophin releasing hormone in amniotic fluid during the third trimester were compared with those of saturated phosphatidyl choline. (2) Corticotrophin releasing hormone levels were measured in a group of normotensive pregnant women during the entire gestation period. Corticotrophin releasing hormone levels during the third trimester were compared in normotensives and patients with pregnancy-induced hypertension.

PATIENTS

Twenty-one non-pregnant normal volunteers and 63 pregnant women.

MEASUREMENTS

Blood pressure, corticotrophin releasing hormone in plasma and amniotic fluid, and saturated phosphatidyl choline in amniotic fluid.

RESULTS

Corticotrophin releasing hormone levels in amniotic fluid samples during the third trimester ranged from 12 to 98 pmol/l and positively correlated with the saturated phosphatidyl choline levels, but not with gestational age. A significant difference existed in plasma corticotrophin releasing hormone concentration between gestational age-matched third trimester normotensive and hypertensive gravids: corticotrophin releasing hormone levels were significantly lower in normotensives (223 +/- 65 pmol/l) than in patients with pregnancy-induced hypertension (544 +/- 106 pmol/l, P = 0.001). Plasma corticotrophin releasing hormone increased with gestational age from 51 pmol/l (range 8.4-85) at 25-32 weeks to 375 pmol/l (range 35-1386) at 33-40 weeks. During the third trimester the rise in plasma corticotrophin releasing hormone conformed to an exponential mathematical model of a positive feedback loop between placental corticotrophin releasing hormone and fetal adrenal cortisol.

CONCLUSIONS

During the third trimester of pregnancy there is a positive correlation between the level of amniotic fluid corticotrophin releasing hormone and that of saturated phosphatidyl choline. The positive correlation between amniotic fluid corticotrophin releasing hormone and saturated phosphatidyl choline, but not between amniotic fluid corticotrophin releasing hormone and gestational age, suggests that a factor(s), such as stress, may affect both amniotic fluid corticotrophin releasing hormone and saturated phosphatidyl choline in parallel. Furthermore, our data are consistent with the hypothesis that the rise in placental corticotrophin releasing hormone is coupled to an increase in fetal glucocorticoid and lung maturation, and that stresses such as pregnancy-induced hypertension may accelerate this process.

Is lung maturation related to fetal growth in diabetic or hypertensive pregnancies?

The purpose of this study was to determine whether infants sufficiently affected by maternal diabetes or hypertension to exhibit abnormal growth (macrosomia, growth retardation) would also display significant alteration in timing of pulmonary maturity (delay or acceleration, respectively). We studied 874 consecutive women with fetal pulmonary maturity testing prior to delivery. Patients were stratified by birth weight into fetal size categories (small for gestational age [SGA], appropriate for gestational age [AGA], large for gestational age [LGA]). Cases were compared based on maternal disease, fetal size categories and pulmonary maturity testing results. Pulmonary maturity rates based on both phosphatidylglycerol (PG) and lecithin/sphingomyelin ratio (L/S) did not differ between term LGA infants of diabetic mothers (97%) and term LGA (80%) or AGA (97%) infants of non-diabetic, non-hypertensive mothers. When compared based on PG alone, there was no difference between the rate of positive PG in term AGA infants of non-hypertensive, non-diabetic mothers (75%) and that seen in the other pregnancy groups (33-80%). Breakdown by gestational age revealed no significant differences in maturity rates between the study groups. Macrosomic diabetic infants and growth-retarded hypertensive infants are no different from controls in their timing of fetal pulmonary maturation.

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.

Pulmonary phospholipids in amniotic fluid of pathologic pregnancies: relationship with clinical status of the newborn

We evaluated phospholipids, C-peptide and cortisol levels in amniotic fluid of 203 pathologic pregnancies (63, class A, B and C diabetics; 11 class D, F and H diabetics; 44 preclampsia and 85 Rh-isoimmunization); the control group was 82 normal pregnant women. There was an acceleration of fetal pulmonary maturation in women with preclampsia and severe Rh-isoimmunization in class D, F and H diabetics (at 34 weeks gestation the incidence of mature surfactant (lecithin/sphingomyelin greater than or equal to 2.7 and presence of phosphatidyl-glycerol) in these groups was 30%, 50% and 100%, respectively, while it was zero in the control group). At 37 and 38 weeks only 44.4% of the class A, B and C diabetics had mature surfactant and there was a significant difference with respect to the control group (x2 = 4.9; p less than 0.05); C-peptide levels in these diabetics (class A, B and C) were higher than in controls (p less than 0.001); in pregnant women with accelerated fetal lung maturation they were lower. We demonstrated a close relationship between fetal pulmonary maturity and the type of surfactant in amniotic fluid, which was independent of gestational age.

A rapid electrochemical assay of lecithin in amniotic fluid using a fluoride ion-sensitive electrode

An electrochemical method is described for the determination of lecithin in rat and human amniotic fluid. Choline is released from lecithin enzymatically by phospholipase D and the hydrogen peroxide released by the action of choline oxidase is quantitatively determined by peroxidase-catalyzed rupture of the covalent C-F bond of 4-fluorophenol. The concentration of F- ions in solutions is determined by a fluoride sensitive electrode from the resulting cell potential difference recorded before and 10 min after addition of a solution containing phospholipase D, choline oxidase and horseradish peroxidase. Lecithin levels in rat amniotic fluid increased from about 10 mumol/l on the 20th day of gestation to 80 mumol/l on day 21, which corresponds to the time of spontaneous delivery. In human amniotic fluid the lecithin concentrations determined with this new method parallel those already reported. They were approximately 10 to 50 mumol/l between the 15th and 18th weeks of gestation and increased from 5- to 7-fold between the 37th and 41st weeks of pregnancy. This method was only slightly influenced by the presence of blood or meconium contamination in the amniotic fluid.

Laboratory and clinical evaluation of a rapid slide agglutination test for phosphatidylglycerol

Amniostat-FLM is a recently developed rapid slide agglutination test for amniotic fluid phosphatidylglycerol. We compared phosphatidylglycerol quantitated by two-dimensional thin-layer chromatography with phosphatidylglycerol determined by Amniostat-FLM in 180 amniotic fluid samples. If any level of phosphatidylglycerol by thin-layer chromatography, including a trace, was considered positive, then phosphatidylglycerol by thin-layer chromatography and Amniostat-FLM were concordant in 171 of 180 samples (95%). Both were positive in 123 and both negative in 48 samples. The nine amniotic fluid samples with discrepant results were as follows: Five negative Amniostat-FLM results were associated with trace phosphatidylglycerol by thin-layer chromatography (1% to 2% of total phospholipids), one negative Amniostat-FLM result was associated with 3% phosphatidylglycerol by thin-layer chromatography, and three positive Amniostat-FLM results were associated with negative phosphatidylglycerol by thin-layer chromatography results. There were 14 samples with trace phosphatidylglycerol by thin-layer chromatography; of these, there were nine positive and five negative Amniostat-FLM results. If greater than 2% phosphatidylglycerol by thin-layer chromatography was considered positive, concordance between the two tests was 93% (167 of 180). From these samples, 119 infants were delivered within 72 hours of amniocentesis. There were 100 positive Amniostat-FLM results and all were associated with the absence of respiratory distress syndrome; of the 19 negative Amniostat-FLM results, five were associated with infants who developed respiratory distress syndrome. The present study confirms that Amniostat-FLM is a simple, rapid, and accurate test for determining the presence of phosphatidylglycerol in amniotic fluid.

Amniotic fluid phosphatidylglycerol in diabetic and control pregnant patients at different gestational lengths

Phosphatidylglycerol (PG) and lecithin/sphingomyelin (L/S) ratios were simultaneously determined in 1770 samples of amniotic fluid. PG was defined as "present" when it appeared in at least 2% of the total phospholipids. Comparison of the appearance of PG in samples of amniotic fluid obtained from diabetic and nondiabetic pregnant patients according to L/S ratios showed that samples from diabetic patients were less likely to have PG present than those from nondiabetic patients, particularly at L/S ratios between 3.1 and 4.0. Because of that, further studies compared the appearance of PG according to gestation in 186 diabetic patients with that in a group of 238 control patients that was composed only of those who underwent repeat cesarean section. Rh-sensitized patients were not included in the control group, since they had delayed appearance of PG. The results showed that the appearance of PG was delayed in patients with Classes B, C, and D-F-R diabetes. In patients with Class A diabetes, the appearance of PG was not significantly different from that in control patients over the entire gestational period, although the appearance of PG may be delayed during early gestation. In contrast, there were no significant differences in L/S ratios in various classes of diabetic pregnant patients and control patients at different gestations.

Amniotic fluid C-peptide and phosphatidyl glycerol in diabetic pregnancy

The concentrations of C-peptide and phosphatidylglycerol in the amniotic fluid were determined in 36 pregnant diabetic women. Twenty-one patients who were being treated with insulin for gestational diabetes as well as 15 patients who were insulin dependent were studied. All patients were subjected to a program of strict metabolic control, and amniocentesis was performed at gestational week 36-37. Phosphatidyl glycerol was present in the amniotic fluid in 15 cases and absent in 21. The mean concentration of C-peptide did not differ whether phosphatidyl glycerol was present or absent. (C-peptide: 0.56 +/- 0.06 and 0.43 +/- 0.05 nmol/l respectively). Although the mean value for amniotic fluid C-peptide in both groups was close to that in diabetic pregnancies with an uneventful neonatal outcome, it was significantly higher than that in non-diabetic pregnancies, indicating minor fetal hyperinsulinemia. The level of C-peptide in the amniotic fluid showed a correlation to the subsequent birthweight of the infant (r = 0.50; p less than 0.01). It is concluded that with rigorous metabolic control of the pregnant diabetic patient, the presence or absence of phosphatidyl glycerol, as an index of fetal lung maturity, is apparently not related to the level of C-peptide in the amniotic fluid.