Doubilet P M, Benson C B
Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA.
J Ultrasound Med. 1995 Jun;14(6):431-4. doi: 10.7863/jum.1995.14.6.431.
Embryonic heart rates below 90 beats per minute at 6 to 8 weeks of gestation have been shown to be associated with a high likelihood of subsequent first trimester demise. The boundary between slow and normal heart rates has not been established, however, in that previous studies do not identify the heart rate for each gestational age at which prognosis plateaus. We evaluated sonograms of singleton pregnancies at 6 to 8 weeks to determine the relationship between heart rate and first trimester outcome in four gestational age subgroups: < or = 6.2, 6.3-7.0, 7.1-7.5, and 7.6-8.0 weeks. Below 6.2 weeks, prognosis improved as heart rate increased to 100 beats per minute, then plateaued for rates > or = 100 beats per minute. At 6.3-7.0 weeks, prognosis improved up to 120 beats per minute, then plateaued. Heart rate norms could not be established at 7.1-8.0 weeks because of the small number of embryonic or fetal deaths in this age group; however, all embryos with heart rates below 110 beats per minute at 7.1-8.0 weeks died. We conclude that the lower limit of normal is 100 beats per minute up to 6.2 weeks' gestation and 120 bpm at 6.3-7.0 weeks.
妊娠6至8周时，胚胎心率低于每分钟90次与孕早期随后死亡的高可能性相关。然而，慢心率与正常心率之间的界限尚未确定，因为先前的研究并未确定每个孕周预后趋于平稳时的心率。我们评估了6至8周单胎妊娠的超声检查结果，以确定四个孕周亚组（≤6.2周、6.3 - 7.0周、7.1 - 7.5周和7.6 - 8.0周）中心率与孕早期结局之间的关系。在6.2周以下，随着心率增加到每分钟100次，预后改善，然后对于心率≥100次/分钟时趋于平稳。在6.3 - 7.0周时，预后改善至每分钟120次，然后趋于平稳。由于该年龄组胚胎或胎儿死亡数量较少，无法确定7.1 - 8.0周时的心率标准；然而，在7.1 - 8.0周时，所有心率低于每分钟110次的胚胎均死亡。我们得出结论，妊娠6.2周及以内正常心率下限为每分钟100次，6.3 - 7.0周时为每分钟120次。
