I like to be right. Who doesn’t? I especially like to be right when I have stuck my neck out to defend my position, been uniformly criticized by smart and well respected scientists and researchers – and then have a study come out which shows I was right all along.
The problem with exercise
I began doing research on infertility
in the late 1980s and focused on the impact of various lifestyle behaviors and emotions on fertility. I founded a mind/body program
for infertility in 1987, based upon some preliminary research, which showed that teaching infertile women various stress-reducing strategies resulted in higher pregnancy rates. As part of the program, I made recommendations about lifestyle changes, based upon the available research. One of the recommendations made to my patients was to decrease the frequency and intensity of their exercise regimen. There hadn’t been any research on the impact of exercise on fertility in humans, but there was some animal research that showed that animals of differing species had lower pregnancy rates when they exercised more.
It made intuitive sense to me. If you go out for a run, you might be running to reduce stress, or to allow yourself dessert that evening. But when you go out for that run, your body thinks you are being chased by a bear. We have the ability to run so that we can escape danger. So if you are running three to five times a week -- although you are doing it to work off the stress from work or so your size 6 pants fit -- your body actually perceives that you are in danger several times per week, and the only reason you are still alive is your ability to outrun that danger. So if your body thinks you are escaping danger so regularly, do you really think that your body is going to allow you to get pregnant, thus making you larger, awkward, slower, and far more vulnerable to that bear?
So for the past 25 years, I have been advising my infertile patients to slow down, to continue to exercise if they want but to try to keep to more modest routines; I suggested walking rather than running, swimming rather than an aerobic class, hatha yoga rather than power yoga, etc. Lo and behold, many of them got pregnant! One of my first success stories was a young woman who had been trying to conceive for several years, including four unsuccessful in vitro fertilization
(IVF) cycles. She was an aerobics teacher. I asked if she could teach without doing, and she decided it was worth a try. She conceived on her own (the old fashioned, more fun way) within two months.
What other experts said
The problem was that no one else seemed to think that exercise was a problem. I would advise my patients to tone down their exercise sessions, but their infertility specialists would tell them to keep it up. Patients would even be encouraged to exercise more to reduce the stress of treatment. Then in 2006, a study came out in the journal Obstetrics and Gynecology. The conclusion of the study was that vigorous exercise was linked with lower pregnancy rates from IVF treatment: “Regular exercise before in vitro fertilization may negatively affect outcomes, especially in women who exercised 4 or more hours per week for 1-9 years and those who participated in cardiovascular exercise.” I was ecstatic, thinking that now we could finally have a consensus in our recommendations for our patients. But not so fast. Most infertility specialists didn’t believe the results, and they criticized the design of the study.
So like a salmon, I continued to swim upstream, maintaining my conviction that vigorous exercise could be harmful for women trying to conceive. In the meantime, I faced disagreement from most everyone else, and was even loudly heckled by a member of the audience when I gave a talk in Chicago which included my recommendation that women consider reducing the intensity of their exercise routine.
The evidence at last
Fast forward to March 16, 2012. The American Society of Reproductive Medicine (ASRM) sent out a bulletin to all 10,000 members, highlighting a new study that indicated that vigorous exercise delayed pregnancy in normal weight women. In this study, Danish researchers followed 3628 women who were planning on becoming pregnant. They completed questionnaires every two months for 12 months or until they achieved pregnancy. For normal weight women, the more vigorous their exercise, the longer it took them to get pregnant. Moderate exercise was associated with the shortest time to conception. There was no relationship for obese women however.
The takeaway? If you are of normal weight and would like to get pregnant, take your exercise routine down a notch. Or two. We still don’t know if the same relationship exists for women who already have infertility and are in treatment, but decreasing one’s exercise intensity is such an easy thing to do, why not?