title: Reduced placental oxygenation during subclinical uterine contractions as assessed by BOLD MRI.
abstract: OBJECTIVE
  During placental Blood Oxygen Level Dependent (BOLD) Magnetic Resonance Imaging (MRI), we have observed spontaneous reductions in placental oxygenation lasting 2-4 min. We hypothesize, that these reductions in placental oxygenation are caused by subclinical uterine contractions.
  
  
  METHODS
  We evaluated placental oxygenation during a five-minute placental BOLD MRI in 56 normal pregnancies (gestational week 23-40) and observed a spontaneous reduction in eight cases. The 56 BOLD MRIs were systematically analyzed for signs of uterine contractions, i.e. visual changes in uterus shape and reductions in the number of pixels within Regions of interest (ROI) covering the outline of the entire uterus.
  
  
  RESULTS
  The eight reductions in the BOLD signal lasted for 217 ± 51 (mean ± SD) seconds with an average signal loss of 17 ± 5%. They were all associated with a contraction, which started 43 ± 21 s prior to the start of the reduction and ended 71 ± 30 s prior to the end of the reduction. In the remaining 48 MRIs, we observed no contraction.
  
  
  CONCLUSIONS
  We suggest that the observed spontaneous reductions in placental oxygenation are caused by uterine contractions. According to our data, subclinical uterine contractions occur regularly and have a markedly impact on placental oxygenation. Therefore, uterine contractions need to be considered in the interpretation of placental MRI as they may interfere with the MRI results.
authors.affiliation: Department of Obstetrics and Gynecology, Aalborg University Hospital, Aalborg, Reberbansgade 15, 9000 Aalborg, Denmark. Electronic address: masore78@hotmail.com.
authors.forename: Marianne
authors.initials: M
authors.lastname: Sinding
authors.affiliation: Department of Clinical Engineering, Central Denmark Region, Aarhus, Olof Palmes Alle 13, 8200 Aarhus N, Denmark. Electronic address: David.Peters@stab.rm.dk.
authors.forename: David A
authors.initials: DA
authors.lastname: Peters
authors.affiliation: Department of Radiology, Aalborg University Hospital, Aalborg, Hobrovej 18-22, 9100 Aalborg, Denmark; Department of Clinical Medicine, Aalborg University Hospital, Sdr. Skovvej 15, 9000 Aalborg, Denmark. Electronic address: jebf@rn.dk.
authors.forename: Jens B
authors.initials: JB
authors.lastname: Frøkjær
authors.affiliation: Department of Obstetrics and Gynecology, Aalborg University Hospital, Aalborg, Reberbansgade 15, 9000 Aalborg, Denmark; Department of Clinical Medicine, Aalborg University Hospital, Sdr. Skovvej 15, 9000 Aalborg, Denmark. Electronic address: obc@rn.dk.
authors.forename: Ole B
authors.initials: OB
authors.lastname: Christiansen
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Aarhus, Palle Juul- Jensens Boulevard 99, 8200 Aarhus N, Denmark. Electronic address: uldbjerg@clin.au.dk.
authors.forename: Niels
authors.initials: N
authors.lastname: Uldbjerg
authors.affiliation: Department of Obstetrics and Gynecology, Aalborg University Hospital, Aalborg, Reberbansgade 15, 9000 Aalborg, Denmark; Department of Clinical Medicine, Aalborg University Hospital, Sdr. Skovvej 15, 9000 Aalborg, Denmark. Electronic address: annenoedgaard@hotmail.com.
authors.forename: Anne
authors.initials: A
authors.lastname: Sørensen
mesh_terms: D015536:Down-Regulation; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000032:analysis / Q000097:blood*; D010920:Placenta / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000378:metabolism; D021041:Placental Circulation / Q000502:physiology; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods; D014590:Uterine Contraction / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: BOLD MRI; Placental MRI; Placental oxygenation; Uterine contraction