title: The effect of clinical characteristics on the lecithin/sphingomyelin ratio and lamellar body count: a cross-sectional study.
abstract: OBJECTIVE
  To study the changes in the lecithin/sphingomyelin (L/S) ratio and lamellar body count (LBC) during pregnancy and to study the effect of clinical characteristics on these measurements.
  
  
  METHODS
  We reviewed in retrospect the amniotic fluid samples for the assessment of fetal lung maturity of consecutive women between January 1996 and December 2000. We evaluated the effect of antenatal administration of glucocorticoids, the presence of diabetes, fetal growth restriction and the amount of amniotic fluid on the L/S ratio and LBC. We then constructed normal curves, by relating the L/S ratio and LBC to gestational age in the cases without respiratory distress syndrome (RDS). Data from the literature were added to these curves.
  
  
  RESULTS
  From the 334 included women, 64 infants (19%) developed RDS. The LBC was lower in women with polyhydramnios (p = 0.04), and similar in women with oligohydramnios. Administration of glucocorticoids, the presence of maternal diabetes or fetal growth restriction did not affect the L/S ratio or the LBC. The median L/S ratio in cases without RDS showed a constant increase from a gestational age of 28 weeks onwards. The median LBC increased slowly between a gestational age of 28 weeks and 34 weeks, to increase more steeply thereafter.
  
  
  CONCLUSIONS
  The amount of amniotic fluid affects the LBC, but not the L/S ratio. Since the L/S ratio and the LBC increase with gestation, differences in gestational age should be taken into account in the interpretation of these fetal lung maturity tests.
authors.affiliation: Department of Obstetrics, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: L D E
authors.initials: LD
authors.lastname: Wijnberger
authors.forename: M
authors.initials: M
authors.lastname: de Kleine
authors.forename: H A M
authors.initials: HA
authors.lastname: Voorbij
authors.forename: B
authors.initials: B
authors.lastname: Arabin
authors.forename: J J C M
authors.initials: JJ
authors.lastname: van de Leur
authors.forename: H W
authors.initials: HW
authors.lastname: Bruinse
authors.forename: G H A
authors.initials: GH
authors.lastname: Visser
authors.forename: P M M
authors.initials: PM
authors.lastname: Bossuyt
authors.forename: B W J
authors.initials: BW
authors.lastname: Mol
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry* / Q000166:cytology; D003430:Cross-Sectional Studies; D005260:Female; D005325:Fetal Organ Maturity / Q000502:physiology*; D005865:Gestational Age; D006785:Hospitals, University; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000196:embryology*; D008499:Medical Records; D009426:Netherlands / Q000453:epidemiology; D010713:Phosphatidylcholines / Q000032:analysis*; D010715:Phosphatidylglycerols / Q000032:analysis; D011237:Predictive Value of Tests; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012127:Respiratory Distress Syndrome, Newborn / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D012189:Retrospective Studies; D013109:Sphingomyelins / Q000032:analysis*
chemical_list: D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D013109:Sphingomyelins