title: The amniotic fluid index in normal twin pregnancies.
abstract: OBJECTIVE
  We sought to investigate the amniotic fluid index for individual gestational sacs of twin pregnancies.
  
  
  METHODS
  Four hundred eighty-eight patients with normal diamniotic twins were examined between 14 and 40 weeks' gestation. The dividing membrane between twin fetuses was identified. An amniotic fluid index was then obtained for each gestational sac.
  
  
  RESULTS
  The median amniotic fluid index in individual twin gestational sacs rises slowly from 14 to 16 weeks' gestation to 23 to 28 weeks' gestation and then gradually declines. The median amniotic fluid index values by gestational age for twin A and twin B are not statistically different. Although twin pregnancies have a slightly lower median amniotic fluid index value than singleton pregnancies, the difference is also not statistically significant.
  
  
  CONCLUSIONS
  Individual amniotic fluid indices can be obtained in twin pregnancies, and the values are comparable with those of singleton gestations.
authors.affiliation: Division of Ultrasound, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Hospital, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Hill
authors.forename: M
authors.initials: M
authors.lastname: Krohn
authors.forename: N
authors.initials: N
authors.lastname: Lazebnik
authors.forename: B
authors.initials: B
authors.lastname: Tush
authors.forename: D
authors.initials: D
authors.lastname: Boyles
authors.forename: J J
authors.initials: JJ
authors.lastname: Ursiny
mesh_terms: D000653:Amniotic Fluid / Q000378:metabolism*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000378:metabolism*; D012016:Reference Values; D014427:Twins