Korean J Obstet Gynecol.  2003 Nov;46(11):2134-2138.

Normal Variation and Predictive Value for Pregnancy Outcome of Fetal Heart Rate in the Early First Trimester

• Kim KY
• Park JS
• Na KH
• Park MH
• Oh KY
• Yang YS
• Hwang IT
• Park JS

Abstract

OBJECTIVE
The purpose of this study was to define the normal variation of fetal heart rate (FHR) and to analyze whether first-trimester fetal heart rate (FHR) are useful in predicting pregnancy outcome.
METHODS
We prospectively studied 162 singleton pregnancies with gestational ages ranging from 5 to 10 weeks between Mar. 1999 and Jan. 2003 visting our hospital. Color doppler sonography was used to calculate the fetal heart rate in beats per minute as the mean of 3 waves.
RESULTS
The following results were obtained. 1. Overall, 149 pregnancies reached viability and 13 resulted in fetal loss before 13 weeks' gestation. 2. A significantly higher number of viable pregnancies, compared with fetal losses, had FHR within one (73.1% compared with 38.5%, p<0.001) and two (94.6% compared with 69.2%, p<0.001) standard deviations of the mean for viable pregnancies at corresponding gestational ages. 3. A significant correlation was seen between gestational age and fetal heart rate (p<0.001). The regressing equation for heart rate was as follows: heart rate = 3.40 X gestational age (days)-30.15 (r = 0.87). 4. There was no significant difference in the fetal heart rates between male and female embryos during this early stage of pregnancy.
CONCLUSION
First-trimester FHR can be helpful to predict pregnancy outcome. Women with FHR outside the reference range from the mean for viable pregnancies at corresponding gestational ages may be at risk for eventual pregnancy loss.

Keyword

Fetal heart rate; Early pregnancy; Fetal sex; Fetal outcome

MeSH Terms

Embryonic Structures
Female
Fetal Heart*
Gestational Age
Heart Rate
Heart Rate, Fetal*
Humans
Male
Pregnancy
Pregnancy Outcome*
Pregnancy Trimester, First*
Pregnancy*
Prospective Studies
Reference Values