title: Changes in spectral power of fetal heart rate variability in small-for-gestational-age fetuses are associated with fetal sex.
abstract: BACKGROUND
  Little is known about the influences of fetal weight and sex on spectral analysis of fetal heart rate (FHR) variability.
  
  
  OBJECTIVE
  The study aims to assess whether there are differences in spectral power of FHR variability according to fetal weight and sex during labor.
  
  
  METHODS
  Case-control study. A total of 414 singleton term deliveries without fetal acidemia were divided into small-for-gestational-age (SGA) (n=29) and non-SGA (n=385) groups. Analyses were performed separately according to fetal sex.
  
  
  METHODS
  FHR recordings obtained with cardiotocography during the last 2h of labor preceding delivery.
  
  
  METHODS
  Our outcome measures include spectral power of FHR variability.
  
  
  RESULTS
  For the male group, SGA fetuses had significantly lower values for low, movement, high, and total frequencies of spectral power compared with non-SGA fetuses (all P<0.005). Normalized low frequency (LFn) was significantly higher, and normalized high frequency (HFn) was significantly lower in SGA fetuses compared with non-SGA fetuses (all P<0.005). In contrast, for the female group, there were no significant differences in any of the indices of spectral power between the SGA and non-SGA fetuses. In addition, SGA males had significantly higher LFn spectral power and lower HFn spectral power compared to SGA females (P=0.016, and 0.041, respectively).
  
  
  CONCLUSIONS
  SGA males have decreased spectral power of FHR variability compared with non-SGA males during labor. However, there are no differences between SGA and non-SGA female fetuses. It is important in the clinical setting to take fetal weight and sex into account during FHR monitoring using spectral analysis.
authors: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, Republic of Korea.
authors: Ji Young
authors: JY
authors: Kwon
authors: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, Republic of Korea; Catholic Congenital Disease Center, The Catholic University of Korea, Seoul, Republic of Korea. Electronic address: ooooobbbbb@catholic.ac.kr.
authors: In Yang
authors: IY
authors: Park
authors: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, Republic of Korea.
authors: Jongil
authors: J
authors: Lim
authors: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, Republic of Korea; Catholic Congenital Disease Center, The Catholic University of Korea, Seoul, Republic of Korea.
authors: Jong Chul
authors: JC
authors: Shin
mesh_terms: D000328:Adult; D015148:Cardiotocography; D016022:Case-Control Studies; D005260:Female; D020567:Fetal Weight; D006340:Heart Rate, Fetal; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000502:physiology*; D008297:Male; D012737:Sex Factors
keywords: Fetal heart rate; Fetal sex; Fetal weight; Small-for-gestational-age; Spectral analysis