title: The "vanishing embryo" phenomenon in an oocyte donation programme.
abstract: BACKGROUND
  We studied the incidence of vanishing embryos (VE) in pregnancies achieved by oocyte donation and evaluated the obstetric and perinatal complications.
  
  
  METHODS
  A retrospective study was carried out based on a chart review of 399 patients with multiple pregnancies from our oocyte donation programme. We defined vanishing phenomenon as the early resorption, in the first trimester, of one or more embryos in a multiple gestation, after confirming embryonic heart activity by transvaginal ultrasound.
  
  
  RESULTS
  Vanishing embryo was observed in 75 patients (18.8%). In 60 patients (80%) this phenomenon occurred before the ninth gestational week. A higher incidence of VE was observed in patients who initially showed a higher number of gestational sacs (P < 0.03). Vaginal bleeding in the first trimester was significantly higher in patients with VE (P < 0.005). Miscarriage rate was similar in pregnancies with and without VE (P = NS). The incidence of pregnancy induced hypertension was decreased in the group with VE (P < 0.03). Preterm spontaneous rupture of membranes occurred more frequently in pregnancies with VE (P < 0.05). However, gestational age at delivery was similar in the group with VE and the controls.
  
  
  CONCLUSIONS
  The high incidence of VE in pregnancies achieved by oocyte donation should be considered when counselling patients with high order multiple gestations.
authors.affiliation: Department of Pediatrics, Obstetrics and Gynaecology, Instituto Valenciano de Infertilidad, Valencia University School of Medicine, C/Guardia Civil 23, 46020 Valencia, Spain. ivivalencia@ivi.es
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodríguez-González
authors.forename: Vicente
authors.initials: V
authors.lastname: Serra
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Garcia-Velasco
authors.forename: Antonio
authors.initials: A
authors.lastname: Pellicer
authors.forename: José
authors.initials: J
authors.lastname: Remohí
mesh_terms: D020964:Embryo Loss / Q000453:epidemiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D015994:Incidence; D008499:Medical Records; D018587:Oocyte Donation; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic