Statement of Dr. Samuel Jacobs, M.D., evaluating Dr. Katherine O’Hagan’s Rabbit Treadmill Study
Statement of Dr. Samuel Jacobs, M.D., evaluating Dr. Katherine O’Hagan’s Rabbit Treadmill Study
My name is Dr. Sam Jacobs, and I am a board-certified obstetrician/gynecologist with 24 years of experience. I have published on the issue of exercise in pregnancy and regularly give clinical advice on exercise to pregnant women at the UMDNJ-Robert Wood Johnson Medical School outpatient clinic. I have reviewed the experimental protocol for Dr. Kathleen O’Hagan’s study “Uterine Circulatory Response to Exercise in Pregnancy,” and as a medical doctor I feel confident in stating that the study is cruel and unnecessary.
Research on exercise and pregnancy prior to the 1980s was generally performed on animals, mainly on pregnant ewes. However, animals react differently to exercise than humans. Most animals pant instead of sweat to get rid of excess body heat. Also, the hemodynamics are different in quadrupeds than in humans, who stand upright. Applying animal research results to human pregnancy has been very limiting. It’s just not possible to make straight extrapolations and assume that what’s true for a pregnant rabbit will be the same for a human female!
Dr. O’Hagan justifies her work by stating that “for ethical and technical reasons, it is difficult to directly investigate the uterine blood flow response to exercise in pregnant women” (NIH Grant Abstract). But her statement ignores the significant amount of human research being done on blood flow in pregnant women. A review of the relevant literature clearly shows that uterine blood flow is regularly measured in women during clinical studies. In fact, there are many studies expressly measuring the effects of exercise on uterine blood flow in women. Consequently, I must strongly disagree with Dr. O’Hagan—her work with rabbits is far from necessary.
When physicians investigate issues of blood flow, they use a noninvasive technology called “Doppler Ultrasound” to measure the systolic velocity of blood flow through a targeted artery. The technology works by measuring the frequency of sound waves reflected off of red blood cells as they flow through the blood stream. Doppler is as simple as it is effective. It is completely safe for pregnant women and is a powerful diagnostic tool.
Using Doppler has enabled countless investigators to research the physiology of exercise in pregnancy in humans, yielding significantly more relevant data than [do] animal models. One such study out of Ireland was the first to look at the effects of confirmed strenuous exercise in an unconditioned population in which the effect of exercise intensity has been described in terms of physiologic measurements on umbilical and uterine artery velocity waveforms. They concluded that a single bout of maximum symptom-limited exercise does not have immediate adverse fetal or maternal cardiovascular effects (Am J Obstet Gynecol 2002;187:661-6).
Another study, from Germany (Ertan, Schanz et al.) used Doppler to study changes in uteroplacental and fetal circulation after maternal exercise in appropriate-for-gestational-age fetuses (AGA) and intrauterine-growth-retarded (IUGR) fetuses. They concluded that maternal exercise does not significantly alter uterine and umbilical perfusion in AGA and IUGR pregnancies, suggesting an absence of change in the uterine vascular bed resistance.
R.U. Erkkola, J.P. Pirhonen, and A.K. Kivejarvi looked at flow velocity waveforms in uterine and umbilical arteries during submaximal bicycle exercise in normal pregnancy [Obstet Gynecol (1992) Apr;79(4):611-5]. This 1992 study used Doppler ultrasound to monitor blood flow in eight healthy women exercised at varying work loads (70, 83, and 92 percent of maximum heart rate). It was found that although uterine blood flow decreased slightly, no change was found in umbilical blood flow to the fetus.
These studies, and others like them, are creating a base of knowledge with which physicians can make responsible clinical judgments.
Today, with the emphasis on physical fitness and the awareness of the benefits of exercise, many women wish to continue or commence exercise during pregnancy. It had been originally hypothesized that the competing demands of exercise and pregnancy could result in impaired blood flow to the placenta and the fetus because of a redistribution of blood flow from the pelvic organs to exercising muscles.
However, the results of over 20 years of clinic research with pregnant women conclusively show that moderate exercise is safe and beneficial during pregnancy. Women show little if any change in uterine blood flow, and there is no significant change to fetal blood flow. It is my professional opinion that animal experiments have added little, if anything, to our medical understanding of the needs of pregnant women and that Dr. O’Hagan’s rabbit experiments will not advance the state of obstetric knowledge.
Samuel L. Jacobs, M.D.
Associate Professor of Obstetrics and Gynecology
UMDNJ-Robert Wood Johnson Medical School
Camden, New Jersey
