Antenatal Steroids and Fetal Lung Maturity
Abstract & Commentary
By John C. Hobbins, MD, Professor of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, COI, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationships relevant to this field of study.
Synopsis: A recent study suggests that infants between 34-39 weeks gestation with immature amniotic fluid lung profiles who are managed expectantly have lower rates of adverse neonatal respiratory outcomes as well as lower rates of overall morbities when compared to infants that are delivered after a course of steroids.
Source: Kamath-Rayne B, et al. Antenatal steroids for treatment of fetal lung immaturity after 34 weeks of gestation: An evaluation of neonatal outcomes. Obstet Gynecol2012;119:909-916.
Apropos of the recent emphasis on discouraging elective deliveries prior to 39 weeks,1 a group from Cincinnati embarked on a study to determine whether steroids had any neonatal benefit in patients delivering between 34 and 39 weeks who had immature amniotic fluid lung profiles.2 The authors reviewed the delivery records between 2005 and 2011 from the busiest hospital in Ohio. They found 982 patients who were between 34 and 39 weeks at the time of their amniocenteses. After applying exclusion criteria (which included previous administration of steroids, IUGR, multiple pregnancies, etc.), they were left with 487 patients who had either:
- A full dose of betamethasone or dexamethasone, given after immature lung profiles (n = 102),
- Expectant management after immature results (n = 76), or
- Mature amniotic fluid lung profiles (n = 184).
A variety of respiratory outcomes and neonatal morbidities were assessed that included the necessity for oxygen supplementation, mechanical ventilation, and surfactant administration. In addition, the authors recorded any hypoglycemia requiring IV infusion, the need for antibiotics, or a requirement for phototherapy for hyperbilirubinemia. Most importantly, they tried to rule out potentially confounding maternal factors such as diabetes, preeclampsia, oligohydramnios, premature rupture of membranes, and other pregnancy complications.
Some of the results were expected. For example, the greatest composite respiratory and neonatal morbidities were higher in the late preterm (34 to 36 6/7 weeks) vs the early term (37 to 38 6/7 weeks) groups. Also, the expectant management group had a longer interval between delivery (10.9 days) vs those with mature lung profiles (1.7 days) and the steroid group (3.5 days post-completion of the steroid course).
The most common reasons for an amniocentesis in this entire study population were a prior cesarean section with a classical incision (15.8%), oligohydramnios or polyhydramnios (14.9%), prior fetal death or abruption (9.9%), or diabetes (9.7%).
The outcome data showed the mature amniocentesis group to have the lowest rates of combined respiratory (3.3%) and overall neonatal morbidities (14%). There was a significant difference in these two dependent variables between the steroid group (9.8% and 26.5%) vs the expectant management group (1.3% and 10.5%), respectively. The authors pointed out that those infants born after expectant management, rather than being delivered after steroids, not only gained an average of 7.5 days more in utero, but also had a 40% reduction in composite neonatal morbidity and a 90% reduction in composite adverse respiratory outcome. Specifically, rates were higher for hypoglycemia, suspected sepsis, need for antibiotics, and prolonged oxygen supplementation in the steroid group.
Commentary
The obvious flaw in the study was that it was not a randomized trial. The reason that the infants did less well in the steroid group could have been that they were perceived clinically to be in greater need for early delivery — e.g., a loaded deck. For example, this group had a lower average birth weight and higher rate of premature rupture of membranes. Realizing this problem, the authors tried to adjust for variables that might influence the provider's desire to pull the trigger. Nevertheless, despite this possible bias, one cannot exclude the possibility that steroids simply were not protective against respiratory distress syndrome (RDS) and might have given the provider a false sense of security that delivery in the late preterm period could be done safely. It is even possible that the steroids might have been at least partially responsible for the neonatal hypoglycemia and sepsis through its metabolic and anti-inflammatory effects, respectively.
A meta-analysis of early randomized clinical trials suggested that the benefits of steroids seemed to stop at 34 weeks,3 and, although one study has shown a maturing of weekly amniotic fluid lung indices when steroids were given between 34 and 37 weeks,4 a recent randomized trial showed no difference in RDS when steroids were given, vs controls, during this period in gestation.5 This is in contradiction to definite benefits of steroids that have been well demonstrated through the years of their use before 34 weeks for prevention of RDS.3,6
Despite the Cincinnati study's warts, the data suggest that if the clinical situation is not deteriorating, the option of watching and waiting in the face of an immature amniotic fluid lung profile at 34 through 38 weeks is preferable to giving steroids followed by delivery.
References
- Fetal lung maturity. ACOG Practice Bulletin No 97. American College of Obstetricians and Gynecologists. Obstet Gynecol 2008;112:717-726.
- Kamath-Rayne B, et al. Antenatal steroids for treatment of fetal lung immaturity after 34 weeks of gestation: An evaluation of neonatal outcomes. Obstet Gynecol2012;119:909-916.
- Crowley PA. Antenatal corticosteroid therapy: A meta-analysis of the randomized trials, 1972 to 1994. Am J Obstet Gynecol 1995;173:322-335.
- Shanks A, et al. Administration of steroids after 34 weeks of gestation enhances fetal lung maturity profiles. Am J Obstet Gynecol 2010;203:47.e1-5.
- Porto AM, et al. Effectiveness of antenatal corticosteroids in reducing respiratory disorders in late preterm infants: Randomised clinical trial. BMJ 2011;342:dl696.
- Liggins GC, Howie RN. A controlled trial of antenatal glucocorticoid treatment for prevention of respiratory distress syndrome in premature infants. Pediatrics1972;50:515-525.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content