title: Risk of late-preterm stillbirth and neonatal morbidity for monochorionic and dichorionic twins.
abstract: OBJECTIVE
  The purpose of this study was to determine the prospective risk of intrauterine fetal death (IUFD) at ≥34 weeks' gestation for monochorionic and dichorionic twins receiving intensive antenatal fetal surveillance. The secondary objective was to calculate the incidence of prematurity-related neonatal morbidity/mortality rates that have been stratified by gestational week and chorionicity.
  
  
  METHODS
  A retrospective cohort study of all twins at ≥34 weeks' gestation who were delivered at the Medical University of South Carolina (1987-2010) was performed. Twins were cared for in a longstanding Twin Clinic with standardized treatment and surveillance protocols and supervised by a consistent Maternal-Fetal Medicine specialist. Gestational age-specific fetal/neonatal mortality rates and composite neonatal morbidity rates were compared by chorionicity. A generalized linear mixed model was used to identify variables that were associated with increased composite neonatal morbidity.
  
  
  RESULTS
  Among 768 twin gestations (601 dichorionic and 167 monochorionic), only 1 dichorionic IUFD occurred. The prospective risk of IUFD at ≥34 weeks' gestation was 0.17% for dichorionic twins and 0% for monochorionic twins. Composite neonatal morbidity decreased with each gestational week (P < .0001). Morbidity was increased by white race, gestational diabetes mellitus, and elective indication for delivery. The nadir of composite neonatal morbidity occurred at 36/0-36/6 weeks' gestation for monochorionic twins and 37/0-37/6 weeks' gestation for dichorionic twins.
  
  
  CONCLUSIONS
  Our data do not support concern for an increased risk of stillbirth in uncomplicated intensively monitored monochorionic twins at ≥34 weeks' gestation. However, our data do show significantly increased rates of neonatal morbidity in late preterm monochorionic twins that cannot be justified by a corresponding reduction in the risk of stillbirth. We believe that our data support delivery of uncomplicated monochorionic twins at 37 weeks' gestation.
authors.affiliation: Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Burgess
authors.affiliation: Department of Obstetrics and Gynecology, Southern Illinois University School of Medicine, Springfield, IL.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Unal
authors.affiliation: Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Nietert
authors.affiliation: Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC.
authors.forename: Roger B
authors.initials: RB
authors.lastname: Newman
mesh_terms: D000328:Adult; D002823:Chorion / Q000503:physiopathology*; D015331:Cohort Studies; D036861:Delivery, Obstetric; D005260:Female; D005313:Fetal Death / Q000453:epidemiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000453:epidemiology*; D008297:Male; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D047928:Premature Birth; D012189:Retrospective Studies; D012306:Risk; D050497:Stillbirth / Q000453:epidemiology*
keywords: delivery timing; dichorionic twins; monochorionic twins; stillbirth