title: Multifetal reduction increases the risk of preterm delivery and fetal growth restriction in twins: a case-control study.
abstract: OBJECTIVE
  To compare pregnancy outcome in twin gestations resulting from multifetal reduction to "primary" twin pregnancies derived from either spontaneous conception or infertility therapy.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  University-affiliated tertiary center.
  
  
  METHODS
  Multifetal pregnancies (quadruplets or more) reduced to twins (group A) compared with twin gestations conceived either spontaneously (group B) or through infertility therapy (group C).
  
  
  METHODS
  Multifetal reduction for group A; perinatal care for groups A, B, and C.
  
  
  METHODS
  Comparison of perinatal complications between groups including antepartum bleeding, premature membrane rupture, and preterm labor. Neonatal outcomes compared including gestational age at delivery, birth weight, incidence of fetal growth restriction, and twin discordancy.
  
  
  RESULTS
  A higher incidence of idiopathic preterm labor was noted in group A cases (14/18) compared with either of the control groups (B: 26/54, or C: 24/54). As a consequence, group A had the lowest gestational age at delivery (32.6 +/- 3.9 weeks) compared with groups B (33.6 +/- 4.4 weeks) and C (36.0 +/- 3.4 weeks). Corresponding birth weights of both first- and second-born twins were significantly lower in group A compared with group C, whereas the birth weight comparison between groups A and B showed a nonsignificant difference. The proportion of pregnancies in which one or both twins weighted less than the 10th percentile was greatest in group A pregnancies (A: 5/18 versus C: 5/54). Discordant birth weight among twin pairs was proportionately greater for group A cases at both the 20% and 30% discordance levels.
  
  
  CONCLUSIONS
  Twin gestations resulting from multifetal reduction are at increased risk for preterm birth, fetal growth restriction, and discordancy when compared with fertility therapy-derived, nonreduced twins.
authors.affiliation: Division of Maternal-Fetal Medicine, Northwestern University Medical School, Evanston Hospital, Illinois, USA. r-silver@nwu.edu
authors.forename: R K
authors.initials: RK
authors.lastname: Silver
authors.forename: B T
authors.initials: BT
authors.lastname: Helfand
authors.forename: T L
authors.initials: TL
authors.lastname: Russell
authors.forename: A
authors.initials: A
authors.lastname: Ragin
authors.forename: J S
authors.initials: JS
authors.lastname: Sholl
authors.forename: S N
authors.initials: SN
authors.lastname: MacGregor
mesh_terms: D000328:Adult; D001724:Birth Weight; D016022:Case-Control Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000209:etiology*; D006801:Humans; D007231:Infant, Newborn; D007752:Obstetric Labor, Premature / Q000209:etiology*; D011247:Pregnancy; D018607:Pregnancy Reduction, Multifetal / Q000009:adverse effects*; D014427:Twins