Pregnancy and Bikram Yoga

As an obstetrician-gynecologist whose primary mode of exercise and personal well-being has become Bikram yoga, I wondered what was out there in terms of research on Bikram yoga and pregnancy.  There has been so few pregnant women attending the classes I’ve been in; I began to wonder if women just stopped during pregnancy. There are no prenatal Bikram yoga classes, so an entire group of women seemed alienated from the practice.  So, what is there in terms of research pertaining to pregnancy outcomes in Bikram yoga practitioners?  Basically nothing!

Given that fact, one has to extrapolate from physiologic changes in pregnancy and those occurring during the Bikram series to make recommendations. Here’s what I’ve concluded to tell my patients who are Bikram yoga practitioners and want to continue during pregnancy.

A woman has to consider that there are numerous changes that take place to maintain a pregnancy.  Briefly, in the first trimester, basal metabolism begins to increase and ultimately requires an increase by as much as 300kcal/day to support mother and growing fetus, while increased rates of filtration at the level of the kidneys can lead to loss of important nutrients (Weissgerber 2006).  The addition of any exercise requires additional calorie intake to support a growing pregnancy.  Blood volume increases but with greater plasma volume than red blood cell volume, resulting in physiologic anemia.  This makes the transport of oxygen to the mother decrease to some degree.  Systemic vascular resistance decreases, leading to a decrease in blood pressure and this leads to an increased heart rate, which nadirs in the second trimester. Decreased blood pressure can lead to decreased blood flow to some important areas of the body such as brain or placenta potentially.  As uterine size increases there is increased pressure on the venous system that can lead to lower extremity swelling, influences respiratory changes that lead to an increased perception of need to breath, and alters a woman’s center of gravity.  All aspects of exercise tolerance. The hormone relaxin leads to musculoskeletal system changes with softening and relaxation of joints in preparation for childbirth, increasing flexility but also increasing risk of injury.

Research now supports that pregnancy should include a component of exercise, as moderate intensity activity has been shown to be beneficial in healthy women with normal pregnancies.  Key in that statement is HEALTHY women with NORMAL pregnancies.  In 2006, a Cochrane Review found 11 studies, with 472 participants, looking at exercise effects on maternal and newborn outcomes (Kramer 2006).  The conclusion was that exercise improved or maintained fitness, but they ultimately determined that data were “insufficient to conclude that exercise during pregnancy influences maternal and newborn outcomes”.  More recently, a Medscape review article, “The Effect of Exercise During Pregnancy on Maternal Outcomes: Literature Review of Exercise During Pregnancy” (Lewis 2008) identified 40 articles including observational and randomized studies and concluded there were reduced rates of hypertensive disorders of pregnancy, gestational diabetes, cesarean section rates, pregnancy symptoms, decreased weight gain, and psychological issues during pregnancy in women who exercised (Morris 2005, Impact 2006).  The American College of Obstetricians and Gynecologists now recommends that women with low risk pregnancies participate in moderate intensity activity, a minimum of 30 minutes, most days of the week (ACOG Committee Opinion).   This does not apply to anyone deemed a high-risk pregnancy and there are obvious activities that pregnant women should avoid such as anything where impact may occur (ie. football, soccer), falls could be sustained (ie. horseback riding, biking) or significant pressure changes encountered (ie. scuba diving).

So, given the physiologic changes in pregnancy and recommendations for some exercise with pregnancy, how does Bikram Yoga fit into this recommendation and what are some of the concerns?  The 90-minute, 26 posture series, can be intense at times especially given the heat of between 95-105 degrees fahrenheit and 40-60 percent humidity.  However, for practitioners who have been doing the series for a minimum of 6 months regularly, there appears to be no reason it can’t be continued with precautions and modifications.  One should proceed with exercise after approval by one’s personal obstetrician-gynecologist, knowledge of your pregnancy by your Bikram yoga instructor, and at the practitioner’s discretion.  The main concerns that arise with practicing Bikram yoga during pregnancy are what occurs with core body temperature during the series.  This is especially true during early pregnancy when the neural tube (ie. central nervous system) is forming.  An additional concern throughout the pregnancy is uteroplacental blood flow with adequate oxygenation, hydration, and substrates to support a growing fetus.

A core body temperature of greater than 102 degrees fahrenheit for more than 10 minutes has been shown to increase risks of neural tube defects in a developing fetus and in a more developed fetus lead to dehydration and potentially reduced amniotic fluid volume.  This most often occurs during fevers but also can be caused by extremely heavy exercise or prolonged exposure to heat sources such as hot tubs or saunas.  Although there are suggestions that extreme temperatures may increase the risks of gastrointestinal and cardiac defects, the only consistently seen defect are those of the neural tube.  Avoiding excessively increased core body temperatures in the first trimester is one way to reduce the risk of neural tube defects, along with taking supplemental folic acid.

The key question is:  If Bikram yoga or ‘hot’ yoga changes core body temperature to above the 102 degrees fahrenheit level for long enough to cause neural tube defects or dehydration in a developing fetus?

Normal range of oral temperatures for females is 36.5-37.3 celsius (97.7-99.1 fahrenheit), with the lowest temperatures being in the early morning hours and peaking in the late afternoon and early evening.  Therefore, ‘hot’ yoga in the morning would be less likely to increase core body temperatures to a concerning level.  Our bodies are expert at regulating and maintaining our core temperature when the surrounding temperature changes, especially if the body grows accustomed to the heat and humidity.  This is one reason why only women who have been practicing Bikram yoga should even consider continuing. This is not a form of exercise I’d suggest starting during pregnancy.  Studies have shown that individuals become acclimatized to heat, developing increased tolerance in hot and humid conditions in 1 to 3 weeks (Guyton, 2006).  The primary way the body maintains the internal temperature in Bikram yoga is through evaporation in the form of sweat glands and dilation of blood vessels, which helps to cool the body.  However, with increasing humidity thermoregulation can be inhibited by limiting sweat evaporation and heat loss (Guyton 2006) and external cooling, with a cool towel or water may aid with temperature regulation.  Increased blood flow to the skin and expanded skin surface area actually have been shown to increase a pregnant woman’s efficiency with temperature regulation, helping her rid her body of excess heat when compared to non-pregnant women.

Over the course of pregnancy, potentially because of an increasing metabolic rate and body surface area, core temperatures have been shown to decrease.  A small longitudinal study of 15 women (GA 8, 16, 26, 36, and 12, 24, 52 weeks postpartum) found maternal core temperature to be highest in the first trimester with a decrease during pregnancy.  At 8 weeks temperatures averaged 37.1 celsius and decreased to term with the nadir of 36.4 celsius at 12wks postpartum, then stabilized by 24 weeks postpartum (Hartgill 2011).  In a general search on the web and in speaking with my yoga instructors, there are many anecdotal stories of women who continued with Bikram yoga during pregnancy without complications.  Simply because there are reports of women and their infants doing fine when the woman practiced Bikram yoga during her pregnancy, does or does not mean it is necessarily not hazardous.  I’d equate it with women who smoke or drink during pregnancy, there are reports of normal pregnancies in those situations as well.  Even initial studies are needed.  Something as simple as a retrospective review of rates of complications in women continuing Bikram yoga practice while pregnant are lacking.

In trying to find information about core body temperature changes during Bikram yoga, one yoga studio conducted an informal “experiment” by having two pregnant women take their oral temperatures before class, three different times during class and again following class.  Neither saw a noticeable rise in temperature, with one reporting lower temperatures during class than at other times during the day.  During another class this studio took the temperatures of 12 non-pregnant individuals before and immediately following class and noted the highest body temperature recorded of 101.5 with an average post-class temperature of 99.7.  However, considering core body temperature differs from oral temperatures by approximately 0.8 degrees, the highest temperature of 101.5 would be above the recommended maximum of 102 degrees. However, we do not know how this fluctuated during class or how long the temperature was maintained.  Although they do not specify women versus men or the time of day these temperatures were taken.  Some general recommendations, if a woman wanted to continue practicing, would be to go in the morning, ask the instructor where the coolest spot in the room may be, drink plenty of fluids to maintain hydration, take a thermometer to monitor one’s temperature during the sequence as everyone will have a different range, take a squirt bottle with cold water in to provide external cooling if necessary, listen to your body by substituting the postures with appropriate pregnancy postures and by taking breaks to cool down and if it requires leaving the class to cool down, yoga etiquette or not, for your safety, exit quietly.

Another issue of concern is uteroplacental blood flow, dehydration and maintenance of nutrients to the fetus throughout Bikram yoga practice.  With increasing basal metabolism and increased filtration at the kidneys it is important that pregnant women maintain adequate nutrition through diet and supplements.  I’ve heard that a session of Bikram yoga burns 600-800 calories for the average woman, increasing calorie intake and taking appropriate supplements is necessary for women to continue practicing.  Eating before class and taking a snack for immediately after would be encouraged.  Even when not pregnant, going to class hydrated and maintaining hydration throughout class is important.  Supplying additional electrolyte rich fluids can help maintain osmotic pressure intravascularly to prevent further decreased blood pressure.  With further vasodilation for cooling, pregnant women may begin to feel light-headed easier as the blood flow is diverted to the skin.  Fetal hemoglobin will insure the fetus will obtain sufficiently oxygenated blood flow but staying well hydrated and sitting if any indication of feeling light headed would be important for mom.

Some general concerns is that first trimester is very critical to fetal development with organogenesis occurring by the end of the twelfth week of gestation.  Any teratogen will have it’s greatest influence at this critical time.  A difficult aspect is that women often don’t know they are pregnant in the very early weeks and because spontaneous miscarriage rates are greater during the first trimester, the legal climate of obstetrics, and often a fear of the unknown, most physicians would likely recommend avoiding many activities in the first trimester.  Rajashree, Bikram’s wife, states that from the second trimester on you can practice her pregnancy yoga sequence.  I was unable to find a statement from Bikram or Rajashree regarding practicing during the first trimester. Think I’ll send her an email.  However, for myself, the thought of not going to Bikram yoga for twelve weeks, if I were to be pregnant, and the effect it would have on my physical and mental well-being would be worth the theoretical risk as long as precautions mentioned above were taken.  Although as I recall during my first pregnancy, from about 7-12 weeks gestation I have never been as tired or nauseous in my entire life so one may not feel up to going to class anyway.  Because of the hormonal mileau wrecking havoc and the energy requirements of the first trimester, there may be times where fewer classes would be in order, more breaks during the series, or incorporating the pregnancy sequence should prevail.

As the pregnancy progresses and the uterus grows, the change of the center of gravity may lead to imbalance during the yoga series.  Taking this into consideration, positioning oneself near a wall, using a bar during some of the series, or adjusting the series as necessary may be required.  Additionally, the hormone relaxin allows for softening of the joints and increased flexibility.  Keeping this in mind, the heat already improves flexibility so women should be particularly cautious when doing postures as to not overstrain or injure themselves by doing something they wouldn’t normally be capable of doing prior to pregnancy.

So, how does the Bikram yoga pregnancy sequence differ?  First, according to the Bikram Yoga Website and Bikram’s wife Rajashree’s pregnancy video she recommends seeking the advice of a doctor before proceeding with Bikram Yoga (I would agree!).  If medically cleared by a physician, without any high risk pregnancy issues, have been practicing Bikram yoga for a minimum of six months, but preferably a year, and plan to continue Bikram yoga throughout your pregnancy then the following adjustments are recommended.  While Rajashree’s pregnancy video provides an alternative sequence and can be done at home, practicing with your normal class requires a few adjustments.   She notes that from the second trimester on you can practice her pregnancy yoga sequence and it can be practiced in a Bikram Yoga Class, but at the pregnant woman’s discretion.


Wishing you health and happiness in your pregnancy. In the end we all want a healthy mom and baby.  Please be certain to seek the advice of your physician to ensure safety during this or any other exercise during pregnancy!

While I am a physician, this article in no way a substitute for someone who knows you well, it an attempt to organize my thoughts for myself and for any patients who may ask me about Bikram in pregnancy.



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