Variables of Fetal Heart Rate and Neonatal Outcome according to Fetal Sex

Han, Dong Ik; Ku, In Sang; Kim, Seong Hee; Koo, Mi Kyung; Hwang, Jeong Hyae; Park, Moon Il; Chung, Sung Ro; Cha, Kyung Joon; Park, Young Sun

Abstract

OBJECTIVE
The differences between two fetal sexes have been a matter of great concern from ancient times to present day. This study was initiated to research the varying fetal behaviors which would differ according to the fetal sex.
METHODS
With every 1,500 cases of each fetal sex selected, the patterns which the varying factors related to FHR and prognosis of neonates in normal pregnancy were compared by means of Factor Analysis (a linear method). Canonical Ensemble was performed to compare the relationship of intrauterine fetal behavioral developments, and neonatal prognosis of each fetal sex. And whether the different types of the fetal sex would have influence also on the chaotic behavior was analyzed by the methods of linear Power Spectrum of FHR and Approximate Enthropy.
RESULTS
The consequences of Factor Analysis showed that it is Apgar score on the factor 1 axis, and signal loss on the factor 2 axis in the case of male babies. In the case of female babies it is Apgar score on the factor 1 axis, and fetal movement on the factor 2 axis. Speaking of the specific value regarding FHR, male babies displayed higher frequency only in terms of fetal movement sign than female babies (p=0.0394). No other differences between two fetal sexes in abnormal findings were indicated (p>0.05). Among the babies at 30~33 weeks' gestation female babies were more likely to reveal higher Canonical Ensemble (male=0.41+/-0.05, female=0.05+/-0.04; p=0.00411), whereas male babies have a higher Approximate Entropy (male=0.926+/-0.01, female=0.871+/-0.01; p=0.0037). However Power Spectrum Analysis indicated that there were no significant differences as I compared LF/HF (p>0.05), the ratio of LF and HF of two fetal sexes, and same result was also drawn by Power Low beta-slope (p>0.05).
CONCLUSION
The linear patterns of the FHR signal from the fetus suggest that there is no variables resulting from the type of fetal sex, except for the fetal movement frequency and the height and weight of neonates. The sympathetic and parasympathetic balance of both fetal sexes also showed a similar development pattern. In the mean time the differences which could be visible were made among the male and female babies specifically at 30~33 weeks' gestation. This may correspond to the fact that the lung maturation of the female fetus is completed before the third trimester of pregnancy, and the male fetus after the period, and finally the differences between the fetal sexes generally become insignificant toward term.