Clinical Articles Predictive value of early embryonic cardiac activity for pregnancy outcome Erik H. Merchiers, MD, Marc Dhont, MD, PhD, Paul A. De Sutter, MD, Cathy J. Beghin, MD, and Dirk A. Vandekerckhove, MD, PhD Ghent, Belgium The biologic variation of the embryonic heart rate was investigated by transvaginal ultrasonography during the first trimester of normal (n = 141) and abnormal (n = 29) pregnancies, and the predictive value of a repeatedly diagnosed slow heart rate for pregnancy outcome was determined. The mean heart rate increased from 82 ± 10.3 beats/min at 5 weeks' gestation to 156 ± 9.6 beats/min at 9 weeks. A single observation of an abnormally slow heart rate did not necessarily predict subsequent embryonic death. However, a continued decline in embryonic heart activity, observed within a few days' interval, was always associated with a first-trimester abortion. (AM J OSSTET GVNECOL 1991 ;165:11-4.)
Key words: Fetal heart rate, first-trimester abortion, transvaginal ultrasonography The earliest proof of a viable pregnancy is obtained when cardiac activity of the embryo can be observed. High-frequency vaginal transducers have improved embryonic imaging in early pregnancy and have facilitated the very early detection of cardiac activity. Several investigators l -3 have reported a gradual increase in embryonic heart rate as detected by ultrasonography starting in the fifth week of pregnancy. Hence, a heartbeat frequency hovering around 100 beats/min may be a physiologic phenomenon in early pregnancy.2.3 There is evidence, however, that an abnormally slow heartbeat is associated with impending embryonic death, 1 but the predictive value of embryonic heartbeat frequency for the evolution of early pregnancy is still unknown. Therefore it was the aim of this study to define the evolution and the biologic variation of early embryonic heart rate between the fifth and twelfth weeks of pregnancy and to correlate abnormally slow heart rates with pregnancy outcome.
Material and methods This study was performed over a 6-month period on 170 pregnancies (fifth through twelfth weeks, 552 obFrom the Department of Obstetrics and Gynecology, University Hospital of Ghent. Received for publication October 18, 1990; revised December 11, 1990; accepted January 18,1991. Reprint requests: Erik H. Merchiers, MD, Department of Obstetrics and Gynecology, University Hospital of Ghent, De Pintelaan 185, B-9000 Ghent, Belgium. 611128061
servations) examined in our ultrasonography department. Patients were referred from either our outpatient or infertility clinic. Of these 170 patients, 146 conceived spontaneously and 24 became pregnant after gamete intrafallopian transfer (n = 5), in vitro fertilization and embryo transfer (n = 16), or zygote intrafallopian transfer (n = 3). Patients were included only when follow-up beyond the first trimester of pregnancy was available and when gestational age was accurately determined by basal body temperature chart, luteinizing hormone surge, or date of ovum pickup. The heart rate was measured by counting heartbeats several times for periods of 15 seconds, averaging, and multiplying by four. All scans were done by the same observer using a 5.0 or 7.5 MHz ATL (Ultramark) vaginal transducer.
Results Of the 170 patients recruited in this study, 141 (14 in vitro fertilization, 5 gamete intrafallopian transfer, 2 zygote intrafallopian transfer) were pregnant, and 29 experienced a miscarriage before week 12. One of those miscarriages was ultrasonographically and histologically diagnosed as hydatidiform mole. In the uncomplicated pregnancies fetal cardiac activity could be detected as early as 5 weeks 3 days (20/24 observations). Between 5 weeks 3 days and 6 weeks cardiac activity was registered in 36 of 42 embryos. Cardiac activity was always detected in the uncomplicated pregnancies from 6 weeks 1 day on (345 observations). Although the em-
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July 1991 Am J Obstct Gynecol
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Key words: Fetal heart rate, first-trimester abortion, transvaginal ultrasonography The earliest proof of a viable pregnancy is obtained when cardiac activity of the embryo can be observed. High-frequency vaginal transducers have improved embryonic imaging in early pregnancy and have facilitated the very early detection of cardiac activity. Several investigators l -3 have reported a gradual increase in embryonic heart rate as detected by ultrasonography starting in the fifth week of pregnancy. Hence, a heartbeat frequency hovering around 100 beats/min may be a physiologic phenomenon in early pregnancy.2.3 There is evidence, however, that an abnormally slow heartbeat is associated with impending embryonic death, 1 but the predictive value of embryonic heartbeat frequency for the evolution of early pregnancy is still unknown. Therefore it was the aim of this study to define the evolution and the biologic variation of early embryonic heart rate between the fifth and twelfth weeks of pregnancy and to correlate abnormally slow heart rates with pregnancy outcome.
Material and methods This study was performed over a 6-month period on 170 pregnancies (fifth through twelfth weeks, 552 obFrom the Department of Obstetrics and Gynecology, University Hospital of Ghent. Received for publication October 18, 1990; revised December 11, 1990; accepted January 18,1991. Reprint requests: Erik H. Merchiers, MD, Department of Obstetrics and Gynecology, University Hospital of Ghent, De Pintelaan 185, B-9000 Ghent, Belgium. 611128061
servations) examined in our ultrasonography department. Patients were referred from either our outpatient or infertility clinic. Of these 170 patients, 146 conceived spontaneously and 24 became pregnant after gamete intrafallopian transfer (n = 5), in vitro fertilization and embryo transfer (n = 16), or zygote intrafallopian transfer (n = 3). Patients were included only when follow-up beyond the first trimester of pregnancy was available and when gestational age was accurately determined by basal body temperature chart, luteinizing hormone surge, or date of ovum pickup. The heart rate was measured by counting heartbeats several times for periods of 15 seconds, averaging, and multiplying by four. All scans were done by the same observer using a 5.0 or 7.5 MHz ATL (Ultramark) vaginal transducer.
Results Of the 170 patients recruited in this study, 141 (14 in vitro fertilization, 5 gamete intrafallopian transfer, 2 zygote intrafallopian transfer) were pregnant, and 29 experienced a miscarriage before week 12. One of those miscarriages was ultrasonographically and histologically diagnosed as hydatidiform mole. In the uncomplicated pregnancies fetal cardiac activity could be detected as early as 5 weeks 3 days (20/24 observations). Between 5 weeks 3 days and 6 weeks cardiac activity was registered in 36 of 42 embryos. Cardiac activity was always detected in the uncomplicated pregnancies from 6 weeks 1 day on (345 observations). Although the em-
11
12
Merchiers et al.
July 1991 Am J Obstct Gynecol
..
y = -91.341+ 8.452
.- 200 I:
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