Significance of fetal heart rate by vaginal ultrasound in the early pregnancy

Cha, Dong Hyun; Lee, Yoon Ho; Kim, Jong Seok; Suh, Seung Hyun; Park, Byung Joo; Kim, Jong Wha

Abstract

OBJECTIVE
Fetal heart rate in embryos(6-8 gestational weeks) have been significantly related to fetal outcome, but have rarely been studied. We attempted to identify fetal heart rate during 6-8 gestational weeks. Our purpose was to determine the lower limit of the heart rate associated with a favorable outcome and to evaluate the prognosis for those embryos with slow heart rates in early period.
METHODS
We prospectively studied 798 singleton pregnancies between Jul. 1997-Dec. 1999 visiting our hospital. Gestational age was calculated from the beginning of the last menstrual period in the case of regular cycle and was confirmed by the crown-rump length. Other cases were measured by crown-rump length or mean gestational sac diameter. Color doppler sonography was used to calculate the fetal heart rate in beats per minute as the mean of 3 waves.
RESULTS
Mean fetal heart rate (+/-SD) were 114.08+/-15.40 bpm for group 1, 126.49+/-18.78 for group 2, 139.83+/-19.92 for group 3, and 149.58+/-23.34 for group 4(p<0.001). Prognosis in the first trimester improved as heart rate increased to 100 bpm in group 1 and 120 bpm in group 2. In group 3 and 4, most of fetus with heart rates below 110 bpm died.
CONCLUSIONS
The fetal heart rate during 6-8 gestational weeks is associated with fetal outcome at the end of the first trimester and we can identify the fetuses that are in risk.