To the Editor:
It continues to bewilder me why articles such as the one by Rauch et al. (1) continue to stratify the embryonic heart rate (EHR) rather than performing a simple regression analysis of the EHR on the embryonic age when it has been shown that there is a linear relationship (2-6). It seems researchers continue to look for a lower threshold for the EHR, when it is obviously age and embryonic size relationship (Figure).
Terry J. DuBose, M.S., R.D.M.S., F.S.D.M.S., F.A.I.U.M.
Associate Professor & Diagnostic Medical Sonography Program Director
University of Arkansas for Medical Sciences, CHRP
Little Rock, Arkansas
1. Rauch ER, Schattman GL, Christos PJ, Chicketano T, Rosenwaks Z. Embryonic heart rate as a predictor of first-trimester pregnancy loss in infertility patients after in vitro fertilization. Fertil Steril 2009; 91:2451-4.
2. DuBose TJ, Cunyus JA, Johnson LF. Embryonic heart rate and age; J of Diagnostic Medical Sonography 1990; 6:151-7.
3. DuBose TJ, Haben-Ansert SL. Obstetric measurements and gestational age in Hagen-Ansert, Textbook of Diagnostic Ultrasound, 6th edition, Vol. 2; Mosby-Elsevier, 2006: 1060-1.
4. DuBose TJ, Miller MM, Moutos DM. Embryonic heart rates compared in assisted and non-assisted pregnancies”; http://www.obgyn.net/us/cotm/0001/ehr2000.htm ; Jan 2000
5. Wisser J, Dirschedl. Embryonic heart rate in dated human embryos. Early Human Development 1994; 37:107-15.
6. Blaas H-GK. The Embryonic Examination. Norwegian University of Science and Technology, TAPIR 1998; ISBN: 82-519-1515-5.
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2009.08.002
The Authors Respond:
We appreciate the comment from Mr. Dubose and the insight that he has provided in this area. We agree that the relationship between embryonic heart rate (EHR) and embryonic age is linear, and we expand on this linear relationship by providing pregnancy outcome data. We offer the following points for clarification: On page 2453 of our manuscript, we discuss the correlation coefficients for assessing the linear relationship between increasing EHR and advancing embryonic age, stratified by the ongoing pregnancy and spontaneous abortion groups. Thus, we did evaluate the relationship of EHR and embryonic age as continuous variables. However, in Table 3 on page 2453, we present the mean EHR for embryonic ages of 4, 5, and 6 weeks for illustrative purposes to emphasize the lack of EHR acceleration in the pregnancy loss group with advancing gestation. More importantly, the relationship between embryonic age and EHR was not the primary focus of our analysis. In Table 2, EHR is stratified to demonstrate the proportion of ongoing pregnancies and pregnancy losses. The multivariate analysis for predictors of poor pregnancy outcome includes EHR as a continuous variable in the logistic model. Therefore, embryonic heart rate independent of maternal or embryonic age is useful to predict poor pregnancy outcome in singleton first trimester IVF pregnancies.
Eden Rauch, M.D., M.P.H.a
Glenn Schattman, M.D.a
Paul Christos, Ph.D.b
Ty Chicketano, M.S.a
Zev Rosenwaks, M.D.a
aCenter for Reproductive Medicine and Infertility
b Division of Biostatistics and Epidemiology
Department of Public Health
Weill Medical College of Cornell University
New York, New York
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2009.08.003