title: Arabin cervical pessary in women at high risk of preterm birth: a magnetic resonance imaging observational follow-up study.
abstract: OBJECTIVE
  To help elucidate the mechanism of action of the Arabin cervical pessary in pregnancies at high risk for preterm delivery.
  
  
  METHODS
  Cervical length and uterocervical angle were evaluated in relation to gestational age in 198 pregnancies not at high risk for preterm birth that underwent clinical fetal magnetic resonance imaging (MRI). Additionally, in 73 singleton pregnancies at high risk for preterm birth, an Arabin cervical pessary was placed at 14-33 weeks' gestation. We performed MRI of the cervix immediately before and after placement and at monthly follow-up until removal of the pessary. In a subgroup of 54 pregnancies with a short cervix and pessary placement at 17-31 weeks' gestation, the uterocervical angle and cervical length at follow-up were compared with the preplacement values.
  
  
  RESULTS
  In pregnancies not at high risk for preterm birth, the uterocervical angle did not vary, but cervical length showed a significant decrease with gestational age (r = -0.15, P < 0.05). Among the high-risk patients, the cervical pessary was successfully placed at first attempt in 60 (82.2%) and by the second attempt in 66 (90.4%), remaining well positioned until removal. In five patients we failed to place the pessary after two attempts, in one patient the pessary dislodged during follow-up and in one case the pessary was partly placed in the external cervical canal and triggered labor the next day. Among the subgroup of 54 patients, the median uterocervical angle immediately after pessary placement was significantly more acute than that prior to placement in the 46 (85.2%) who delivered after 34 weeks (132° vs 146°, P < 0.01), but was unchanged in the eight patients who delivered before 34 weeks (143° vs 152°, P > 0.05).
  
  
  CONCLUSIONS
  In patients at high risk for preterm delivery, correct placement of the Arabin cervical pessary should be checked immediately; this can be performed quickly and easily using MRI. This study provides some evidence that, in singleton pregnancies with a short cervix, a cervical pessary delays birth through a mechanical effect on the uterocervical angle.
authors.affiliation: Department of Radiology, University Hospital Brugmann, Brussels, Belgium; Department of Radiology, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: M M
authors.initials: MM
authors.lastname: Cannie
authors.forename: O
authors.initials: O
authors.lastname: Dobrescu
authors.forename: L
authors.initials: L
authors.lastname: Gucciardo
authors.forename: B
authors.initials: B
authors.lastname: Strizek
authors.forename: S
authors.initials: S
authors.lastname: Ziane
authors.forename: E
authors.initials: E
authors.lastname: Sakkas
authors.forename: F
authors.initials: F
authors.lastname: Schoonjans
authors.forename: L
authors.initials: L
authors.lastname: Divano
authors.forename: J C
authors.initials: JC
authors.lastname: Jani
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D010570:Pessaries; D011247:Pregnancy; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D047928:Premature Birth / Q000517:prevention & control*; D011446:Prospective Studies; D012189:Retrospective Studies; D014591:Uterine Diseases / Q000628:therapy*; D055815:Young Adult
keywords: Arabin pessary; cervical pessary; magnetic resonance imaging; observational study; preterm birth