title: Evaluation of normal neurological development of human fetuses from 21 to 30 weeks' gestation through fetal auditory evoked response.
abstract: OBJECTIVE
  To evaluate the neurological maturation of fetuses between 21 and 30 weeks' gestation by the auditory evoked response.
  
  
  METHODS
  The auditory evoked responses of 25 normal singleton fetuses were observed once a week from 21 to 30 weeks' gestation. The stimulus consisted of five pulses of sinusoidal waves, for 2 s, at 1500 cycles/s, with a sound pressure of 125 dB.
  
  
  RESULTS
  Fetal auditory evoked response increased with neurological maturation, presenting two main points of positive discontinuity. The two points in the heart response were detected between the 24(th)/25(th) and the 27(th)/28(th) week. From the 27(th) week on, fetal motor response (FMR) was always present. Initial fetal heart response presented a fluctuation pattern between the 21(st) and the 30(th) week, with a tendency to increase as gestational age advanced. Fetal heart response also increased with gestational age. Late response (LR) fluctuated until the 29(th) week, and was always present after that period.
  
  
  CONCLUSIONS
  The maturation of the fetal nervous system is clearly demonstrated by changes in the auditory evoked responses in different gestational ages, and presents some discontinuity points.
authors.affiliation: Department of Gynecology and Obstetrics of Medical School Pontifical Catholic University of Rio Grande do Sul, Rio Grande do Sul, Brazil. sergioheckerluz@hotmail.com
authors.forename: Sérgio Hecker
authors.initials: SH
authors.lastname: Luz
authors.forename: Fabiano Candal
authors.initials: FC
authors.lastname: Vasconcellos
authors.forename: Tatiana
authors.initials: T
authors.lastname: Kreling
authors.forename: Fernanda Silva
authors.initials: FS
authors.lastname: Pacheco
authors.forename: Márcia Lorena Fagundes
authors.initials: ML
authors.lastname: Chaves
mesh_terms: D005072:Evoked Potentials, Auditory; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D006801:Humans; D008297:Male; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D013216:Reflex, Startle