title: Does fetal sex influence the risk of preterm delivery in dichorionic twin pregnancies after spontaneous conception?
abstract: OBJECTIVE
  The incidence of preterm delivery has been increasing, and our aim was to estimate the influence of fetal sex on the risk of preterm delivery in dichorionic twins after spontaneous conception.
  
  
  METHODS
  125 spontaneously conceived dichorionic twin gestations, with viable fetuses, born after 24 weeks and delivered spontaneously before 37 weeks, were enrolled. The impact of fetal sex, previous preterm delivery, maternal age, body-mass-index, smoking, and parity on gestational age at birth were evaluated.
  
  
  RESULTS
  Despite similar baseline characteristics in all three groups, women with one or two male fetuses delivered significantly more often before 34 weeks than patients with two female fetuses, 48% (23/48) and 43% (19/44) vs 21% (7/33), p = .04. Regression analyses, including fetal sex, maternal age, maternal body-mass-index, smoking, previous preterm delivery and parity, revealed that only fetal sex was significantly associated with spontaneous preterm delivery (p = .03).
  
  
  CONCLUSIONS
  Fetal sex appears to be a risk factor for preterm delivery in spontaneously conceived dichorionic twin gestations. Twin pregnancies with one or two male fetuses seem to be at higher risk for spontaneous preterm delivery than those with only females.
authors.affiliation: Department of Obstetrics and Feto-maternal Medicine, Medical University of Vienna, Vienna, Austria. katharina.klein@meduniwien.ac.at
authors.forename: Katharina
authors.initials: K
authors.lastname: Klein
authors.forename: Christof
authors.initials: C
authors.lastname: Worda
authors.forename: Maria
authors.initials: M
authors.lastname: Stammler-Safar
authors.forename: Peter
authors.initials: P
authors.lastname: Husslein
authors.forename: Norbert
authors.initials: N
authors.lastname: Gleicher
authors.forename: Andrea
authors.initials: A
authors.lastname: Weghofer
mesh_terms: D000328:Adult; D001317:Austria; D005260:Female; D005306:Fertilization; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology* / Q000235:genetics*; D012044:Regression Analysis; D012307:Risk Factors; D012727:Sex Characteristics; D014429:Twins, Dizygotic / Q000235:genetics*; D055815:Young Adult