title: Dizygotic twin pregnancy after transfer of one embryo.
abstract: OBJECTIVE
  To consider the risk of intercourse without contraception during infertility treatment.
  
  
  METHODS
  Case report.
  
  
  METHODS
  Leiden University Medical Center.
  
  
  METHODS
  An infertile couple underwent IVF for tubal pathology.
  
  
  METHODS
  Transfer of one embryo during a natural cycle.
  
  
  METHODS
  Human leukocyte antigen typing, histochemical analysis of the fetal membranes, neonatal and maternal clinical outcomes.
  
  
  RESULTS
  A dizygotic twin pregnancy was confirmed after birth by human leukocyte antigen typing of both fetuses and mother and by histochemical analysis of the dividing fetal membranes. This suggests a pregnancy of concurrent IVF and spontaneous conception. Pregnancy was complicated by preeclampsia and intrauterine growth retardation of both fetuses.
  
  
  CONCLUSIONS
  We state that couples should abstain from intercourse without contraception during infertility treatment to prevent multiple gestation and its related complications for mother and fetuses.
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands. m.l.p.van_der_hoorn@lumc.nl
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: van der Hoorn
authors.forename: Frans
authors.initials: F
authors.lastname: Helmerhorst
authors.forename: Frans
authors.initials: F
authors.lastname: Claas
authors.forename: Sicco
authors.initials: S
authors.lastname: Scherjon
mesh_terms: D000328:Adult; D005260:Female; D005306:Fertilization / Q000502:physiology; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011272:Pregnancy, Multiple; D056826:Single Embryo Transfer; D014429:Twins, Dizygotic