The heart rate during 6-8 weeks' gestation is associated with fetal outcome at the end of the first trimester and identifies those embryos that are in jeopardy. Embryos with heart rates below 85 beats/ min during 6-8 weeks' gestation did not survive. A highly significant (p < 0.01) linear decrease was seen in fetal losses with increasing gestational age. In groups 3 and 4, a heart rate of 146 beats/min or more was associated with the fewest losses (5.5% and 3.3%, respectively). The average heart rate for baby boys in the first trimester was 154.9 bpm (plus or minus 22.8 bpm) and for baby girls it was 151.7 bpm (plus or minus 22.7 bpm). A heart rate between 116 and 125 beats/min was associated with the fewest losses in groups 1 (10.8% losses) and 2 (8.6%). Statistically significant differences (p < 0.01) in the mean heart rates were seen between all groups. M-mode sonography was used to calculate the embryonic heart rate as the mean of at least 3 waves in beats/minute. Gestational age was calculated from the known date of the beginning of the last menstrual period and was confirmed by sonographic measurement of the crown-rump length. This study analysed data from a large cohort of 30,416 singleton pregnancies with normal outcomes from a Chinese population, aiming to construct reference intervals for gestational sac diameter (GSD), yolk sac diameter (YSD), heart rate (HR) and CRL at 610 gestational weeks (GW) following IVF-ET. We prospectively studied 2,164 singleton pregnancies between 19.
We also tried to determine the lower limit of the heart rate associated with a favorable outcome for each group.
We attempted to identify embryonic heart rates at 4 stages during 6-8 weeks' gestation and to relate our findings to fetal outcome at the end of the first trimester. Heart rates in embryos (6-8 weeks' gestation) have rarely been studied.
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