Amniocentesis for fetal lung maturity has historically been performed for many reasons: Even though the risks associated with third trimester amniocentesis are extremely low, complications have been documented, including preterm labor, placental abruptions, intrauterine rupture, maternal sepsis, fetal heart rate abnormalities, and fetal-maternal hemorrhage. This review presents the types of tests for fetal lung maturity, presents the indications and tests utilized, and discusses recommendations for when amniocentesis for fetal lung maturity may be appropriate.
Management of complicated high-risk pregnancies continues to evolve. Since the discovery of ultrasound and antenatal Amniocentesis for fetal lung maturity testing, increasing emphasis has been placed on optimizing fetal outcomes. Recently, authorities have questioned the efficacy of assessing fetal lung maturity. The advantage of this procedure is that it can help prevent respiratory distress syndrome RDS if fetal lung maturity testing is positive. This review presents the types of tests for fetal lung maturity, presents the indications and tests utilized, and discusses the complications of the procedures.
We discuss the controversy surrounding the use of tests for fetal lung maturity that has recently been raised.
Our goal as obstetricians should be to optimize the outcomes of both the mother and the fetus. In an attempt to determine if fetal lung maturation has occurred to a point sufficient to avoid the development of fetal RDS, numerous tests have been developed. The different tests are based on the following four basic themes: Limitations of this test are that blood and meconium interfere with the Amniocentesis for fetal lung maturity, 56 it is difficult to perform, and the test is time consuming.
Initially, testing for PG was also done with thin-layer chromatography, but the development of a rapid slide agglutination test simplified matters. The level of polarization is lower as more surfactant is present. This was initially described by Shinitzky and associates in This test is currently not available commercially.
Other tests have been described.
Saturated phosphatidylcholine uses thin layer chromatography and is valid with blood and meconium. The shake test was initially described by Clements and associates in The foam stability index is a semi-quantitative version of the shake test. The tubes are shaken for 30 seconds and allowed to rest for 15 seconds. Blood and meconium are associated with false mature results. The tap test involves the breakdown of bubbles in an earlier layer.
This test involves adding 1 mL of amniotic fluid to 1 drop of 6N hydrochloric acid and 1. Simply looking at the turbidity of amniotic fluid has been studied. Sbarra and associates 24 published an article regarding untrained observers who were able to correctly identify mature versus immature unspun amniotic fluid samples.
The optical density
Amniocentesis for fetal lung maturity amniotic fluid at mm has also been studied.
This test may be used with blood present, but not with meconium. Lamellar body count LBC is a simple, test for determining fetal lung maturity. Type II pneumocytes store surfactant in lamellar bodies, which are then secreted into the alveolar spaces.
These structures are similar in size to platelets, allowing for automated counting by hematologic counters. It should be noted, however, that despite consensus paper, different analyzers use different methods for counting platelets, and specific cutoffs need to be developed for each analyzer.
Campbell 32 used the biparietal diameter in as an early attempt to predict lung maturity based on ultrasound measurements. Expanding on the tissues examined, Podobnik and colleagues 34 looked at the coefficient of variation of the grey levels of placentas, fetal lungs, and fetal livers, as predictors of pulmonary maturity. Recently, fetal pulmonary artery Doppler has been used to predict neonatal RDS. Kim and coworkers 35 found that an elevated acceleration-to-ejection time ratio was significantly associated with neonatal RDS.
Table 1 reviews the available tests for determining fetal lung maturity. All of the tests used to evaluate fetal lung maturity by amniocentesis have been shown to have good sensitivity proportion of immature tests results in neonates with RDS and negative predictive values probability of no corresponding RDS with a mature fetal lung maturity test result.
They also suggested that analyzer-specific cutoffs are required, and should be confirmed with outcome-based studies by each laboratory offering the test.
The aforementioned tests have another problem in common, which is the fact that they have used a single cutoff value regardless of gestational age to determine fetal lung maturity. Parvin and associates 45 confirmed this relationship 1 year later. Karcher and coworkers 46 not only found similar results with the surfactant-to-albumin ratio, but with the LBC as well. Historically, amniocentesis has been used to evaluate fetal lung maturity for a variety of medical and obstetric indicators with the plan to deliver the mother if fetal lung maturity is documented.
All of the indications that have been reported in the literature are presented in Table 2. Table 3 summarizes all of the data on fetal lung maturity published to date. Interestingly, what one center uses as indicators for an amniocentesis, others do not. This lack of consistency suggests that as obstetricians became more comfortable with the procedure more assessments were performed, thus expanding the indications for the procedure.
This expansion of indications could explain the increase in late preterm deliveries we see in the United States, because centers are performing amniocentesis on patients early and delivering the patients if maturity is documented.
The preponderance of evidence reported in the literature over the past several years indicates that neonatal morbidity is increased, regardless "Amniocentesis for fetal lung maturity" a positive fetal lung maturity test result in infants born prior to 39 weeks of gestation.
The consensus and findings were published Amniocentesis for fetal lung maturity August Conversely, if delivery could be postponed in the event of an immature test result, the patient lacks a sufficient indication for delivery in the first place. Based on this consensus, the indications for amniocentesis to determine fetal lung maturity have been significantly narrowed.
In fact, one could argue that the only remaining indications are restricted to those patients in whom accurate fetal dating is absent.
The American Congress of Obstetricians and Gynecologists ACOG considers one of the following criteria to be necessary in Amniocentesis for fetal lung maturity to consider a pregnancy to be at term: In addition, in patients with poor dating and with indications for late preterm or early-term delivery, amniocentesis for fetal lung maturity may be of benefit in Amniocentesis for fetal lung maturity the timing of some deliveries Table 2.
Over the years, indications for amniocentesis for fetal lung maturity have changed. During most of this time, they have expanded. However, in light of recent data and the increasing use of biophysical profiles and Doppler ultrasound, this trend has been reversed. One of the problems of using a mature biochemical test for fetal lung maturity as an indication for delivery is that such a test does not assure the absence of other morbidities, or, as discussed earlier, respiratory problems when delivering an infant before 39 weeks of gestation.
Two studies have looked at composite risk for late preterm and early term infants as compared with infants born at 39 weeks.
These composite indices, although slightly different, included admission to the neonatal intensive care unit, treated hypoglycemia and hyperbilirubinemia, presumed or confirmed sepsis, ischemia encephalopathy, periventricular leukomalacia, and death, as well as adverse respiratory outcomes.
Bates and colleagues 3 found that infants born at 39 weeks had a 2. The recommendation Amniocentesis for fetal lung maturity amniocentesis with placental or uterine complications such as placenta previa, placenta accreta and its variants, previous classical cesarean delivery, or myomectomy has virtually disappeared. If there is an urgent fetal or maternal need for delivery, it should be performed.
Otherwise, it is recommended that patients with placenta previa be delivered at 36 to 37 weeks, 48 and those with placenta accreta, increta, and percreta be delivered at 34 to 35 weeks.
Another major category that was used in the past as an indication
Amniocentesis for fetal lung maturity amniocentesis is fetal complications, including fetal growth restriction, fetal anomalies, and multiple gestations. It is now recommended that fetuses with uncomplicated fetal growth restriction be delivered at 38 to 39 weeks, as long as fetal well-being is assured.
With twin gestations, delivery should take place between 32 and 38 weeks, depending on the chorionicity, whether the twins are monoamniotic or diamniotic, and if other complications exist.
Previously, maternal comorbidities or complications such as chronic hypertension, preeclampsia, and diabetes have been indications for amniocentesis for fetal lung maturity. Women with chronic hypertension, without superimposed preeclampsia and other maternal or fetal complications, should be delivered between 36 and 39 weeks, depending on whether they are on medication or not and if their blood pressures are controlled. Those with pregestational diabetes who have vascular disease and well-controlled blood sugars may be delivered as early as 37 weeks.
The above recommendations assume no other comorbidities and a reassuring fetal status. The last major category that has been used as an indication for amniocentesis for fetal lung maturity involves obstetrical complications.
Patients with preterm premature rupture of membranes PPROM at 34 weeks or later should be delivered at the time of diagnosis. Mercer and colleagues performed a prospective randomized trial in patients with PPROM with documented fetal lung maturity between 32 and 36 weeks and randomized them to expectant management or immediate delivery. Suggesting knowledge of fetal lung maturity Amniocentesis for fetal lung maturity be advantageous in patients with this complication.
Patients in spontaneous preterm labor at 34 weeks or later should be delivered only if labor is progressive or there are other maternal or fetal indications for delivery. It is currently not recommended to deliver patients with a history
Amniocentesis for fetal lung maturity unexplained stillborn deliveries and without other complicating factors in the current pregnancy before 39 weeks. If late preterm
Amniocentesis for fetal lung maturity early term delivery before 39 weeks is considered, then amniocentesis for fetal lung maturity should be performed.
The last indication would be patients delivered for poor dating. An ACOG Bulletin recommends that prior to elective delivery in patients who do not meet the criteria of a well-dated pregnancy, fetal lung maturity be confirmed by an amniocentesis after 39 weeks by the best date the physician has.
That said, there may be a place for amniocentesis when gestational age is not well documented. National Center for Biotechnology InformationU. Journal List Rev Obstet Gynecol v. Author information Copyright and License information Disclaimer.
This article has been cited by other articles in PMC. Abstract Amniocentesis for fetal lung maturity has historically been performed for many reasons: Types of Tests for Fetal Lung Maturity In an attempt to determine if fetal lung maturation has occurred to a point sufficient to avoid the development of fetal RDS, numerous tests have been developed.