title: Diagnostic techniques and criteria for first-trimester conjoined twin documentation: a review of the literature illustrated by three recent cases.
abstract: OBJECTIVE
  Conjoined twins are rare. High-quality imaging techniques are essential for proper first-trimester diagnosis. Technological development leads to new imaging techniques such as 3-dimensional virtual embryoscopy. The aim of this review was to explore imaging techniques used in the first-trimester diagnosis of conjoined twins and provide a systematic diagnostic table for making this diagnosis.
  
  
  METHODS
  A PubMed literature search was performed using the terms ultrasound, Doppler, MRI, and CT combined with first-trimester and conjoined twins. Three recent cases at our department are reviewed and examined additionally using 3-dimensional virtual embryoscopy.
  
  
  RESULTS
  The different types of conjoined twins are summarized in a table for practical use during ultrasound examination. In evaluating conjoined twins, 2-dimensional ultrasound is the criterion standard. Three-dimensional and Doppler ultrasounds add anatomical and prognostic information. Virtual embryoscopy imaging reveals additional findings in our 3 cases not seen with routine 2-dimensionalultrasound examination.
  
  
  CONCLUSIONS
  Each case of conjoined twins is unique and should be evaluated with the best possible imaging techniques. Three-dimensional and Doppler ultrasound should be added to the systematic diagnostic evaluation of conjoined twins. Virtual embryoscopy imaging may contribute to earlier, more appropriate counseling and management of these pregnancies.
authors.affiliation: PhD Student, Division of Obstetrics and Prenatal Medicine, Department of Obstetrics and Gynaecology.
authors.forename: Leonie
authors.initials: L
authors.lastname: Baken
authors.forename: Melek
authors.initials: M
authors.lastname: Rousian
authors.forename: Erwin J O
authors.initials: EJ
authors.lastname: Kompanje
authors.forename: Anton H J
authors.initials: AH
authors.lastname: Koning
authors.forename: Peter J
authors.initials: PJ
authors.lastname: van der Spek
authors.forename: Eric A P
authors.initials: EA
authors.lastname: Steegers
authors.forename: Niek
authors.initials: N
authors.lastname: Exalto
mesh_terms: D000328:Adult; D004282:Documentation; D005260:Female; D005332:Fetoscopy / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D014057:Tomography, X-Ray Computed; D014428:Twins, Conjoined; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult