title: Ultrasound screening for fetal growth restriction at 36 vs 32 weeks' gestation: a randomized trial (ROUTE).
abstract: OBJECTIVE
  To compare the utility of routine third-trimester ultrasound examination at 36 weeks' gestation with that at 32 weeks in detecting fetal growth restriction (FGR).
  
  
  METHODS
  This was an open-label parallel randomized trial (ROUTE study) conducted at a single general hospital serving a geographically well-defined catchment area in Barcelona, Spain, between May 2011 and April 2014. Women with no adverse medical or obstetric history and a singleton pregnancy without fetal abnormalities at routine second-trimester scan were assigned randomly to undergo a scan at 32 weeks' gestation (n = 1272) or at 36 weeks' gestation (n = 1314). Primary outcome measures were detection rates of FGR (customized birth weight < 10(th) centile) and severe FGR (customized birth weight < 3(rd) centile).
  
  
  RESULTS
  There were no significant differences in perinatal outcome between those who underwent a scan at 32 weeks' gestation and those who underwent a scan at 36 weeks' gestation. Severe FGR at birth was associated significantly with emergency Cesarean delivery for fetal distress (odds ratio (OR), 3.4 (95% CI, 1.8-6.7)), neonatal admission (OR, 2.23 (95% CI, 1.23-4.05)), hypoglycemia (OR, 9.5 (95% CI, 1.8-49.8)) and hyperbilirubinemia (OR, 9.0 (95% CI, 4.6-17.6)). Despite similar false-positive rates (FPRs) (6.4% vs 8.2%), FGR detection rates were superior at 36 vs 32 weeks' gestation (sensitivity, 38.8% vs 22.5%; P = 0.006), with positive and negative likelihood ratios of 6.1 vs 2.7 and 0.65 vs 0.84, respectively. In cases of severe FGR, FPRs for both scans were also similar (8.5% vs 8.7%), but detection rates were superior at 36 vs 32 weeks' gestation (61.4% vs 32.5%; P = 0.008). Positive and negative likelihood ratios were 7.2 vs 3.7 and 0.4 vs 0.74, respectively.
  
  
  CONCLUSIONS
  In low-risk pregnancies, routine ultrasound examination at 36 weeks' gestation was more effective than that at 32 weeks' gestation in detecting FGR and related adverse perinatal and neonatal outcomes.
authors.affiliation: Obstetrics and Gynecology Department, Althaia, Network Healthcare Manresa Foundation, Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Roma
authors.affiliation: Research and Innovation Unit, Althaia, Network Healthcare Manresa Foundation, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Arnau
authors.affiliation: Obstetrics and Gynecology Department, Althaia, Network Healthcare Manresa Foundation, Barcelona, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Berdala
authors.affiliation: Obstetrics and Gynecology Department, Althaia, Network Healthcare Manresa Foundation, Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Bergos
authors.affiliation: Research and Innovation Unit, Althaia, Network Healthcare Manresa Foundation, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Montesinos
authors.affiliation: BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine, Hospital Clínic and Hospital Sant Joan de Déu, IDIBAPS, University of Barcelona and Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Figueras
mesh_terms: D000328:Adult; D001724:Birth Weight / Q000502:physiology; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D051556:Hyperbilirubinemia, Neonatal / Q000453:epidemiology; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D018615:Ultrasonography, Doppler, Color / Q000379:methods; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014469:Umbilical Arteries / Q000000981:diagnostic imaging
keywords: fetal development; fetal growth restriction; neonatal complications; placenta; ultrasonography