title: Clinical evaluation of the risk of twin-to-twin transfusion syndrome using the relative power contribution of fetal heart rate fluctuations.
abstract: OBJECTIVE
  In twin pregnancies, it has been suggested that fluctuations of the two fetal heart rates should be considered as two variates that affect each other. We therefore investigated whether the relative power contribution (RPC) of heart rate fluctuation between twins reflects the clinical severity of twin-to-twin transfusion syndrome.
  
  
  METHODS
  Sixty-three cases of twin pregnancy including 43 monochorionic twins and 20 dichorionic twins were studied. Thirteen monochorionic twins with polyhydramnios in one twin were regarded as twin-to-twin transfusion syndrome (TTTS). Of the 13 TTTS cases, 8 cases with polyhydramnios in one twin and oligohydramnios in the other were deemed to be a 'stuck' twin. The RPC of the very low frequency domain (VL; 0.0125-0.0625 Hz) of fetal heart rate fluctuation in the twin fetuses of monochorionic and dichorionic pregnancies was obtained within a week of delivery. The relationship between the value of the RPC and the outcome of these twins was examined.
  
  
  RESULTS
  For both monochorionic and dichorionic twins the RPC of twin fetuses was significantly higher in TTTS twins than in twins without TTTS. In particular, in pregnancies that resulted in fetal death, early neonatal death, or hydrops of one of the twins, this twin had a higher RPC than the other twin. No significant difference was observed in the RPC value between twins of either monochorionic or dichorionic pregnancies that did not develop TTTS. Serial changes in RPC values were followed in 7 cases of TTTS. The RPC value rose rapidly just before delivery in three cases with resultant poor outcome.
  
  
  CONCLUSIONS
  A rapid change in the RPC of twin fetuses measured using the VL frequency domain of fetal heart rate fluctuations may predict poor outcome in twin pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Aobaku, Sendai, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kimura
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Suzuki
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Sugawara
authors.forename: Takashi
authors.initials: T
authors.lastname: Murakami
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Terada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Chisaka
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Okamura
mesh_terms: D005260:Female; D005313:Fetal Death / Q000209:etiology; D005330:Fetofetal Transfusion / Q000150:complications / Q000209:etiology* / Q000503:physiopathology*; D006340:Heart Rate, Fetal; D006801:Humans; D016104:Oligohydramnios / Q000150:complications; D006831:Polyhydramnios / Q000150:complications; D011247:Pregnancy; D011256:Pregnancy Outcome; D011379:Prognosis; D012307:Risk Factors; D012720:Severity of Illness Index; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic