What is the best measure of fetal lung maturity?
Fetal lung maturity Respiratory distress syndrome of the newborn infant caused by immaturity of the fetal lung continues to be a clinical problem. Measurement of pulmonary surfactant production is the most effective way to evaluate pulmonary maturity. Since the first fetal lung maturity test was described more than two …
What is amniocentesis for fetal lung maturity?
Amniocentesis for fetal lung maturity has historically been performed for many reasons: uterine and placental complications, maternal comorbidities, fetal issues, and even obstetric problems.
What is the LBC test for pneumocytes?
Lamellar body count (LBC) is a simple, rapid test for determining fetal lung maturity. Type II pneumocytes store surfactant in lamellar bodies, which are then secreted into the alveolar spaces.
What is a normal lamellar body count for pulmonary maturity?
Lamellar body counts of 50,000 per microliter or greater suggest pulmonary maturity. However, results are instrument-dependent and need to be validated in individual laboratories. Test results are affected by blood and meconium when they are present in the AF.
What causes respiratory distress in infants?
It is most commonly caused by a deficiency in pulmonary surfactant due to premature birth. The pulmonary surfactants are needed to help reduce the surface tension in the alveoli of the infant lung and prevent the alveoli from collapsing. There are other more rare causes of RDS including genetic defects that cause altered production of surfactant proteins. RDS is the most common cause of respiratory failure in neonates and occurs with increasing frequency with decreased gestational age such that it is very common in infants born before 28 weeks and very rare in term infants. It’s estimated that approximately 20,000 infants develop RDS each year in the United States. The best way to avoid RDS is to prevent premature birth.
How long does it take for a newborn to have RDS?
As I mentioned already, predicting the risk that an infant will have RDS if delivered within 72 hours of when testing is performed can be done by assessing the surfactants present in AF. This testing is really only useful between 32 and 39 weeks of gestation. Prior to 32 weeks, the infant stands the risk of other morbidities associated with pre-term birth such as intracranial hemorrhage, inability to eat, or maintain body temperature, etc. FLM testing should only be performed if delivery is desired, but could be safely delayed. The American College of Obstetricians and Gynecologists (ACOG) guidelines do not recommend FLM testing if delivery is mandated for fetal or maternal indications. If delivery is imminent or if delivery must occur in order to prevent morbidity or mortality in the mother, then there is no point in FLM testing. These tests allow physicians to make decisions about delivery by weighing the risk to mom of not delivering vs the risk to baby of delivering. As a screening tool, these tests must have high sensitivity to detect RDS so that infants are not inappropriately delivered only to develop respiratory distress.
How to measure surfactant to albumin ratio?
The surfactant to albumin ratio can be measured using fluorescence polarization. A fluorophore is added to the AF. It can attach to albumin, which slows its rotation. It moves more rapidly when it is associated with the phospholipids. The change in polarization, which is a function of how rapidly a fluorophore is rotating, depends on the microviscosity of the solution. An elevated surfactant/albumin ratio has been correlated with the presence of FLM; the threshold for maturity is 55 mg of surfactant per gram albumin. Test results are affected by blood and meconium when they are present in the AF. This was a commercially available kit. However, production of this kit has been discontinued.
Why are surfactants needed in the lungs?
The pulmonary surfactants are needed to help reduce the surface tension in the alveoli of the infant lung and prevent the alveoli from collapsing . There are other more rare causes of RDS including genetic defects that cause altered production of surfactant proteins.
What is agglutination test?
A commercially available agglutination test for the qualitative detection of PG is available. PG from the AF is incorporated into lipid particles. Anti-PG antibodies are then added. If PG is present in the AF, then there is agglutination of the lipid particles. Visible inspection of the agglutination reaction is conducted to determine the presence or absence of PG. The results from this test are qualitative and reported as either “negative”, “low” positive, or “high” positive. Testing results are not affected by blood and meconium when they are present in the AF.
Is a PG test valid in blood?
However, if the PG is performed by TLC and expressed as a ratio of PG/S, the test is not valid in the presence of blood, since sphingomyelin is present in blood. PG has the disadvantage of being the last lipid to increase in surfactant (around gestational week 36).
Can you get FLM if you have a fetal pregnancy?
The American College of Obstetricians and Gynecologists (ACOG) guidelines do not recommend FLM testing if delivery is mandated for fetal or maternal indications. If delivery is imminent or if delivery must occur in order to prevent morbidity or mortality in the mother, then there is no point in FLM testing.
How does ultrasound help with amniotic fluid?
Your belly is clean ed with a solution that prevents infection. Your healthcare provider uses ultrasound images to help guide a thin needle through your belly, into the uterus, and to the area where the most amniotic fluid is . Like when you have your blood drawn, you may feel some brief, mild discomfort from the needle.
What is the last organ to mature in a baby before birth?
The lungs are the last organs to mature in a baby before birth. A fetal lung maturity test checks your baby’s lungs to see if the baby will be able to breathe OK if he or she is born early. A very thin needle is used to remove a small amount of fluid from the amniotic sac. The amniotic sac is the bag of fluid that surrounds the baby.
What is done to obtain amniotic fluid for lung maturity testing?
Amniocentesis is done to obtain amniotic fluid for lung maturity testing in any of the following situations: 1. Before repeat cesarean delivery, if fetal lung maturity is in doubt. 2. In the case of preterm labor, to aid in the decision of whether to initiate tocolysis. 3.
What is the full range of lung maturity?
Mammals display the full range of lung maturity at birth from the Muridae and dogs, where alveolarization is entirely postnatal, to the guinea pig where the full complement of alveoli appears to be present at birth. Likewise, it is clear that in some species (mice, rats, primates, pigs, rabbits) new alveoli form into early adulthood while in other species postnatal neoalveolarization is limited (guinea pigs, sheep) ( Figure 1 ). There still remain significant gaps in our knowledge of species-specific changes in lung structure with age, and research is required in this field. In particular, studies on the “normal” changes in lung structure into senescence are warranted. In species that are kept under controlled conditions (e.g., mice, rats), it appears as though the aged lung is characterized by increased collagen deposition with no alveolar destruction, which is consistent with fibrotic pathology (depending on which strain is used). In contrast, in species where environmental exposures and infection are not controlled (e.g., dog, nonhuman primates), there is evidence of emphysematous changes in lung structure in the latter stages of life ( Figure 1 ). Of course, in the case of the Muridae there will still be environmental stimuli, however, these will be vastly different to the exposures of the other species and this needs to be considered when investigating age-related changes in lung structure.
What is amniocentesis used for?
Amniocentesis may be performed to obtain amniotic fluid for white blood cell count, Gram's stain and culture, or rapid tests for infection described later in Section IV.
How much phosphatidyl glycerol is present in fetal lung?
Fetal lung maturity should be verified in such cases from the presence of more than 3% phosphatidyl glycerol or the equivalent in amniotic fluid as ascertained from an amniocentesis specimen.
What is the amnio dye test?
Amniocentesis is most commonly indicated for prenatal diagnosis and for fetal lung maturity. Other indications include amnioreduction, diagnosis of an intraamniotic infection, confirmation of preterm premature rupture of membranes, evaluation of hemolytic anemia in the fetus, diagnosis of hemoglobinopathy, and diagnosis of neural tube defects. Indigo carmine has been used in the “amnio dye test” to confirm ruptured membranes in the past; however, widespread shortages in the availability of this agent and the absence of a suitable substitute have made this test impractical. The guidance is similar to that used during cordocentesis to evaluate for fetal platelet count, anemia, and blood type.
Does stress cause lung maturation?
The concept of stress suggests elevated fetal catecholamine and corticoid levels, agents that can cause accelerated lung maturation; however, many agents seem to effect lung maturation and no agent to date can predictably prevent RDS in all infants. Table 3. Some Pregnancy-Related Conditions Affecting Lung Maturation.
