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Amniocentesis for fetal lung maturity testing

Published:December 18, 2013DOI:https://doi.org/10.1016/j.ajog.2013.12.023
      To the Editors:
      We read with great interest the editorial by Towers, et al
      • Towers C.V.
      • Freeman R.K.
      • Nageotte M.P.
      • Garite T.J.
      • Lewis D.F.
      • Quilligan E.J.
      The case for amniocentesis for fetal lung maturity in late-preterm and early-term gestations.
      regarding amniocentesis for fetal lung maturity (FLM) testing in the late preterm period for delivery planning. We had 3 concerns with the authors' argument.
      First, although the authors discussed respiratory distress syndrome (RDS) and common short-term morbidities in the newborn period, they failed to mention the significant long-term risks associated with late preterm birth, including increased infant mortality and impaired neurodevelopment,
      • Kugelman A.
      • Colin A.A.
      Late preterm infants: near term but still in a critical developmental time period.
      consequences commonly underestimated by obstetricians. Of note, the 34 week brain is only 65% of term brain weight and volume,
      • Kugelman A.
      • Colin A.A.
      Late preterm infants: near term but still in a critical developmental time period.
      making the late preterm period a time of critical importance in neurodevelopment. Increasing evidence supporting these risks should be weighed in decisions regarding delivery timing.
      Second, the authors do not report the weaknesses of FLM testing, apart from the fact that lung maturity is not equivalent to overall maturity. Amniotic fluid FLM testing has high negative predictive value for postnatal absence of RDS; however, approximately 50% of infants with immature FLM testing do not have RDS. Further, RDS risk can be as high as 8% in 34 week newborns despite mature FLM testing,
      • Pinette M.
      • Blackstone J.
      • Wax J.
      • Cartin A.
      Fetal lung maturity indices—a plea for gestational age-specific interpretation: a case report and discussion.
      indicating substantial opportunity exists for improving FLM testing.
      Finally, the authors state that antenatal corticosteroids (ANCS) followed by delivery for immature FLM indices is a possible treatment option. We feel clinical equipoise remains regarding benefit of ANCS administration after 34 weeks gestation. Our previous work evaluated outcomes of infants who received ANCS after immature fetal lung indices and were subsequently delivered within 1 week. Compared with expectant management with later delivery or waiting until mature FLM testing, respiratory morbidity was highest following ANCS administration and delivery than with the other management approaches. Furthermore, infants with immature FLM followed by ANCS and delivery had higher rates of hypoglycemia and sepsis evaluation, indicating this approach may incur some newborn risk.
      • Kamath-Rayne B.
      • DeFranco E.
      • Marcotte M.
      Antenatal steroids for treatment of fetal lung immaturity after 34 weeks of gestation: an evaluation of neonatal outcomes.
      Even if ANCS were effective to reduce RDS risk at later preterm gestational ages, considering a baseline risk of RDS of 15% in newborns greater than 34 weeks' gestation, the number needed to treat is quite high, approximately 145 to prevent 1 case of RDS.
      • Sinclair J.
      Meta-analysis of randomized controlled trials of antenatal corticosteroid for the prevention of respiratory distress syndrome: discussion.
      The Maternal-Fetal Medicine Units Network ALPS trial is underway to assess the benefit of ANCS administration at >34 weeks. Considering the unknown risk-benefit ratio of ANCS following immature FLM testing for delivery planning purposes, we urge caution with this practice until clinical trial results are available.

      References

        • Towers C.V.
        • Freeman R.K.
        • Nageotte M.P.
        • Garite T.J.
        • Lewis D.F.
        • Quilligan E.J.
        The case for amniocentesis for fetal lung maturity in late-preterm and early-term gestations.
        Am J Obstet Gynecol. 2014; 210: 95-96
        • Kugelman A.
        • Colin A.A.
        Late preterm infants: near term but still in a critical developmental time period.
        Pediatrics. 2013; 132: 741-751
        • Pinette M.
        • Blackstone J.
        • Wax J.
        • Cartin A.
        Fetal lung maturity indices—a plea for gestational age-specific interpretation: a case report and discussion.
        Am J Obstet Gynecol. 2002; 187: 1721-1722
        • Kamath-Rayne B.
        • DeFranco E.
        • Marcotte M.
        Antenatal steroids for treatment of fetal lung immaturity after 34 weeks of gestation: an evaluation of neonatal outcomes.
        Obstet Gynecol. 2012; 119: 909-916
        • Sinclair J.
        Meta-analysis of randomized controlled trials of antenatal corticosteroid for the prevention of respiratory distress syndrome: discussion.
        Am J Obstet Gynecol. 1995; 173: 335-344

      Linked Article

      • The case for amniocentesis for fetal lung maturity in late-preterm and early-term gestations
        American Journal of Obstetrics & GynecologyVol. 210Issue 2
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          The recent American College of Obstetricians and Gynecologists Committee Opinion no. 560 and the Society of Maternal-Fetal Medicine article argue for the abandonment of fetal lung maturity (FLM) testing.1,2 We concur with the conclusion that the timing of delivery in certain complicated obstetric conditions can be complex and that a risk management decision must be made. This process involves considering the risks to the neonate from premature birth vs maternal and fetal risks that are associated with pregnancy continuation.
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        American Journal of Obstetrics & GynecologyVol. 210Issue 6
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          Drs Kamath-Rayne and DeFranco have addressed 3 primary concerns with our recent editorial regarding the case for using amniocentesis in the management of complicated pregnancies that are late-preterm and/or early-term. In response to the first concern of potential long-term concerns for preterm neonates, we are not proposing the “elective” delivery of 34 weeks' gestations or any late-preterm and/or early-term pregnancy before 39 weeks' gestation. This should only occur if a clinical disorder suggests that delivery may be better than nondelivery for the mother or the fetus, especially if we can anticipate a benign neonatal course.
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