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Complementary and Alternative Medicine Series

Prenatal Yoga
What You Need to Know

Mary T. Jackson, MD, MBA

Serena Jones is a 29-year-old G3 P0020, LMP unknown. Her baby’s gestational age by first trimester ultrasound is 16 2/7 weeks. Her general health is good, and social history negative for smoking, physical abuse, or drugs of any kind. She has been an avid exerciser for several years, engaging in aerobic dance and weight lifting. Her medical/surgical history is negative other than the two prior first-trimester spontaneous abortions. She presented for a routine prenatal exam.

Serena has a question. She’s excited and happy to be pregnant, glowing, in fact. She wants to know if you’ll just sign this form for her. She hands you a piece of paper. It’s a consent form from Serena’s health club signed by her yoga instructor. They want to know if it’s safe for Serena to take a yoga class. They want your written permission.

Now what?

Perhaps you are 1 of the 18 million people in this country already practicing Hatha Yoga. After all, more than 75% of mainstream health clubs offer yoga among their range of activities. If so, you will be at a distinct advantage when discussing “corpse pose” and “inversions” with your patients.

According to the Wall Street Journal, 23% of Americans say they do yoga, meditation, or other stress-relieving activities regularly. Of those who practice yoga, 68% are women, 75% between the ages of 25 and 54 years. With statistics like these, someone in your patient population will want your advice, and possibly your consent. Are you ready to discuss the benefits and risks of prenatal yoga?

Should you just sign the consent form? Should you refuse outright and warn your pregnant patient about quackery and sham? If you’ve been in practice long enough, you will remember when the second response would have been standard of care. Today’s more “enlightened” environment has made us all more tolerant of, if not completely enthusiastic about, complementary and alternative practices. Decades ago, any exercise beyond a short walk was frowned upon during pregnancy. In 1994, the American College of Obstetrics and Gynecology (ACOG), in the face of both public demand and solid research evidence, relaxed their guidelines cautiously. At that time, we were told “there currently are no data to confirm that, with the specific exceptions mentioned here, exercise during pregnancy has any deleterious effects on the fetus.”1 Adding a conservative bottom line, “…no level of exercise during pregnancy has been conclusively demonstrated to be beneficial in improving perinatal outcome.”1 Certainly ACOG was not promoting vigorous exercise for pregnant women in 1994.

In January 2002, ACOG’s Committee on Obstetric Practice published a new document reflecting emerging clinical and scientific advances it felt the practicing obstetrician should be aware of. The committee’s tone had changed over the years from one of cautious assent to one of encouragement. Today, ACOG tells us that “…30 minutes or more of moderate exercise a day on most, if not all, days of the week is recommended for pregnant women.”2

Evidence-based medicine has caught up with popular trend. Exercise in the absence of medical or obstetric complications has been studied extensively in women of all fitness levels from the elite athlete who wishes to maintain her strict training schedule during pregnancy3 to the well-intentioned couch potato. We are now learning that even the most sedentary primigravida in our practice can safely benefit from vigorous exercise, significantly improving her aerobic fitness,4 and possibly avoiding common medical complications of pregnancy such as gestational diabetes.5,6

Why all the fuss over exercise in the first place? Why have we historically been so conservative in our recommendations?

Specific concerns, those warnings first heard from our residency mentors, continue to come to mind. Many of these have now been addressed.

Exercise-induced hyperthermia: Is it a teratogen?

We may have read those classic studies of the 1980s associating increased maternal core temperature during animal embryogenesis with cessation of neuronal mitotic cell growth in the developing brain.7 Perhaps we remember the “hot tub studies” of the 1990s that linked observed increases in congenital anomalies with early pregnancy heat exposure.8

Remember the old saying, “Pregnant women are neither rats nor guinea pigs?” You may have used it yourself a few times when addressing the latest flurry of media-driven anxiety founded on animal research. Sure enough, human studies have now shown that in fit women there is a fetoprotective thermal response, which, interestingly, is enhanced by exercise.9 Peak rectal temperatures following exercise to 64% of maximum oxygen consumption actually decreased by 0.3°C at 8 weeks, falling further, at a rate of 0.1°C per month, until 37 completed weeks of gestation.9,10 The ACOG Committee Opinion of 2002 sites this saying, “There have been no reports that hyperthermia associated with exercise is teratogenic.”2 This leaves hot tubs and superheated rooms still in question. But, what about premature labor? What about intrauterine growth restriction? Isn’t it true that heavy exercise before term can bring on these two common societal and personal tragedies?

Hemodynamic studies have shown clearly that exercise can cause a decrease in splanchnic circulation.11 This “splanchnic steal syndrome” shunts blood away from internal organs, including the uterus, sending it to the working muscle, skin, and adrenals. It has been feared, and widely taught as fact, that decreased myometrial oxygen delivery can stimulate uterine contractions. In addition, decreased blood flow to the uterus was felt to reduce fetal nutrition, possibly leading to intrauterine growth retardation. If maternal exercise can lead to poorly grown infants suffering preterm labor and delivery, surely it should be avoided.

The well-known 30% to 50% increase in cardiac output associated with pregnancy results in an increase of regional, gestational-age dependent, blood flow to the pregnant uterus in a range of 2- to 20-fold.12 Meanwhile, stroke volume and end-diastolic volume increase, as systemic vascular resistance decreases. These changes mimic the physiologic response to chronic exercise. It is felt that in fit gravidas, like Serena, the effects are complementary. Bottom line: Current studies show that moderate aerobic exercise does not reduce uterine blood flow to the extent necessary to impair fetal outcome.

An interesting pair of clinical research studies by Clapp, a doctor responsible for much elegant basic science research in this field, was published separately in the Journal of Pediatrics in 1996 and in the American Journal of Obstetrics and Gynecology in 1998. In these two studies Clapp and colleagues outlined the morphometric and neurodevelopmental outcomes of the offspring of women who exercised regularly throughout pregnancy both at 1 year and again at 5 years of age.13,14

Exercise was found in these studies to cause neither impairment nor dramatic improvement. Outcomes were similar between those women who exercised regularly and those who did not. The only significant difference found was in the body composition of the neonates. It appears that high-volume, moderate-intensity, exercise in midpregnancy to late pregnancy symmetrically reduces fetoplacental growth with a proportionally greater decrease in neonatal fat mass over lean body mass.15 These leaner babies suffered no adverse consequences. It has, in fact, been proposed that a decrease in neonatal fat mass may aid the developing adult in maintaining normal weight, avoiding obesity, in later life.15

A more recent prospective observational study of 750 low-risk active-duty women attending the Naval Medical Center prenatal clinic in San Diego, Calif, confirmed Clapp’s findings. Compared with the infants of nonexercising mothers, the infants of the most strenuously exercised women were 86.5 g (+ 43.7g) lighter. Significantly, from a clinical perspective, this trend continued into the group of light exercising mothers as well with no difference detected in APGAR scores or other markers of neonatal health between groups.16

But what about spontaneous abortion? Serena has already lost two early pregnancies. Could her exercise program be responsible for these losses?

Based upon the research of Clapp, and others,17-19 Williams Obstetrics has this to say: “Continuation of aerobic exercise at intensities between 50% and 85% of their maximum capacity…had no effect on the incidence of spontaneous abortion.”20 Furthermore, a review of the literature published as recently as 2000 found no reports suggesting an increase in the incidence of placental abnormality, congenital malformation, or infertility among women who continue strenuous exercise throughout early pregnancy.21 The recently published study from Naval Medical Center San Diego confirms earlier studies: “…pregnancy loss is not correlated with the level of exercise.”16

Scientific evidence, therefore, gives a green light on continuing aerobic exercise throughout an uncomplicated pregnancy. But what about yoga? Will Serena be tying herself in knots, standing on her head, and holding her breath for long periods? Possibly. Yoga can include each of these practices. As her physician you need to know several important things:

  • What type of yoga is your patient going to be practicing?
  • Is the instructor conducting a class specifically for pregnant women?
  • Does the instructor have any training in prenatal yoga or in the physiologic changes of pregnancy?
  • Will traditional postures (asanas) be modified to accommodate physical changes as pregnancy progresses?

Most yoga studios and athletic clubs in the west concern themselves with the practice of Hatha Yoga. Hatha encompasses the many forms of yoga that use physical postures, often linked with breathing techniques, to enhance mental and spiritual awareness. Hatha yoga can vary greatly in its physical intensity. A class generally lasts from 30 minutes to 2 hours and can range in difficulty from the intense handsprings, headstands, and pretzel twists of advanced Ashtanga to the gentle stretches and hip openers of Restorative yoga. You’ll never know which end of the spectrum your patient’s yoga class falls into unless you know enough to ask.

Here are a few important questions you might ask Serena before you sign the form. Even if she doesn’t know the answers and has to do a bit of research, she will appreciate your time and your obvious caring.

You might even go one step further and telephone the prospective prenatal yoga instructor to get a feel for the approach being used. It may turn out to be a valuable form of practice marketing for both of you.

Q: How does your teacher modify supine postures like “corpse pose” for pregnancy?

Corpse pose is usually the last pose. In it one lies supine on their mat relaxing completely for at least 5 minutes.

Prenatal modifications include lateral recumbent (Fetal Pose) and semireclining positions (Reclining Queen.)

Q: What kind of props will your class be using?

Chairs are used in many classes, especially in third trimester.

The teacher using chairs, bolsters, blankets and other props has safety in mind, has probably taken a prenatal yoga training course, and has thought through appropriate modifications.

Health clubs may not have actual yoga props for their instructors to use. A well-trained instructor can still lead a safe and beneficial prenatal class without props; it’s just more difficult.

Q: How does your teacher feel about practicing inversions, twists, full forward folds, and intense breathing exercises during pregnancy?

Inversions (shoulder stand, headstand, handstands, plow pose) are controversial. Many teachers avoid them in pregnancy.

Full body twists and complete forward folds are not recommended.

Breath holding and Val Salva maneuvers are not recommended.

Q: Does your teacher offer special poses or a special class for use after delivery?

Postpartum classes are catching on and sometimes even include babies.

Not only do these classes encourage continued exercise, they act as support groups for new mothers, possibly decreasing postpartum depression.

A list of various Hatha Yoga Styles are described in the above Table. Of course, this list is not inclusive. Kriya, Anusara, Tantra, Kirtan, Sivananda, Shadow, and Hidden Language styles, to name a few, have been left out. Studios and health clubs may offer classes that are a mix of various techniques. Class styles depend upon what and where the teacher has studied. Pure Ashtanga and Bikram are the notable exceptions.

Teacher certification and experience are extremely variable. Some may be teaching yoga after only a weekend course. Others have spent years and thousands of dollars learning and perfecting their craft.

Yoga Alliance, in Reading Pa, is the best-known certification group in the United States today. It maintains a registry of certified instructors and is making a serious attempt to establish high standards among its members.

Not every experienced instructor will be registered; some feel it is unnecessary and refuse to join (sort of like doctors joining the American Medical Association). But if a yoga teacher is registered with Yoga Alliance, you know they have completed over 200 hours of study. That’s a good start.

So, before you sign Serena’s consent form, do a little checking. The best way to find out what sort of exercises your patients are doing is to speak with their instructor.

Hatha Yoga Styles

Ashtanga is the most athletic style. In it, flowing dance-like movements are repeated between each of a specific series of poses. These poses are done in tandem with the breath, rather rapidly, and together can resemble an aerobic workout. The true Primary Series, as easy as it sounds, contains several poses not suitable for beginners, and would be quite impossible for a pregnant woman. Adaptations of Ashtanga can be found in Power Yoga, Jivamukti, and in Vinyasa Flow classes.

Bikram is also known as “hot yoga.” This style uses 26 specific and invariable poses, including supine poses, and two breathing techniques, one of which is similar to hyperventilation. The room in which these rather vigorous postures are performed is superheated, often above 100°F. Bikram teachers are known for encouraging students to greatly exert themselves during class and many students love it.

Iyengar Style, developed by BKS Iyengar, emphasizes precision and form. Props are used extensively. The teacher training required to become a certified Iyengar instructor is excellent. It takes 2 years. An Iyengar-based Prenatal Class would be expected to be carefully designed and quite safe. The safety of inversions (upside-down poses like shoulder and headstands) is often questioned and remains controversial among instructors. While many feel they are best avoided in pregnancy, Iyengar’s own daughters have been beautifully photographed doing inversions when obviously pregnant.

Kripalu Yoga combines the classic poses of Hatha Yoga with mental and emotional introspection and release. It is deep and meditative, designed to relieve tension and to heal the emotional problems represented or created by physical stress.

Kundalini Yoga teachers may follow the Sikh pathway, wearing white turbans and robes. Their poses are different from classical style. They place emphasis on various breathing techniques that are felt to release the energy stored in the base of the spine. Kundalini researchers, a number holding MDs and PhDs, have done a lot to further scientific study into the possible benefits of yoga and meditation on the immune system. They also have a rather famous prenatal program attended by Madonna and other celebrities at the Golden Bridge Studio in Hollywood, Calif.

Integral Yoga attempts to combine all yogic paths. It is more meditative than physical. It teaches spiritual awareness that can be brought into daily life.

Viniyoga instructors attempt to “size up” their students’ needs, offering adaptations and modifications of classic poses designed to fit each individual safely and with maximum benefit. Medical problems and physical conditions, including pregnancy, are considered on a personal basis. This form of instruction would be expected to be quite safe.

Restorative Yoga is not a separate school but rather a practice taken from other schools, principally Iyengar. Gentle, comforting poses, using the support of props help reduce stress and relax physical stiffness. Prenatal classes generally tend to be highly restorative. Stress reduction and stretching is the goal and this is what pregnant woman often say they want most from a yoga class.
Mary T. Jackson, MD, MBA, FACOG, practices office gynecology and yoga in central California.

REFERENCES

  1. American College of Obstetricians and Gynecologists. ACOG Technical Bulletin no. 189. Washington, DC: ACOG, 1994.
  2. American College of Obstetricians and Gynecologists. Exercise During Pregnancy and the Postpartum Period. ACOG Committee Opinion no. 276, January 2002.
  3. Hale RW, Milne L. The elite athlete and exercise in pregnancy. Semin Perinatol. 1996;20:277-284.
  4. Marquez-Sterling S, Perry AC, Kaplan TA, Halberstein RA, Signorile JF. Physical and psychological changes with vigorous exercise in sedentary primigravidae. Med Sci Sports Exer. 2000;32(1):58-62.
  5. Dye TD, Knox KL, Artal R, Aubry RH, Wojtowycz MA. Physical Activity, obesity, and diabetes in pregnancy. Am J Epidemiol. 1997;146(11):961-965.
  6. Jovanovic-Peterson L, Peterson CM. Exercise and the nutritional management of diabetes during pregnancy. Obst Gynecol Clin N Am. 1996; 23(1):75-86.
  7. Edwards MJ. Hyperthermia as a teratogen: a review of experimental studies and their clinical significance. Teratogenesis Carciog Mutagen. 1986;6(6):563-582.
  8. Milunsky A, Ulcickas M, Rothman KJ, Willett W, Jick SS, Jick H. Maternal heat exposure and neural tube defects. JAMA. 1992;268(7):882-885.
  9. Yeo S. Thermoregulatory adjustment during pregnancy protects fetus from exposure of exercise-induced hyperthermia. Eur J Thermol. 1997:7(3):119-126.
  10. Clapp JF III. The changing thermal response to endurance exercise during pregnancy. Am J Obstet Gynecol. 1991;165(6 pt 1):1684-1689.
  11. Saltin B, Rowell LB. Functional adaptations to physical activity and inactivity. Fed Proc. 1980;39(5):1506-1513.
  12. Clapp JF. Exercise during pregnancy. In: Bar-Or O, et. al. Perspectives in Exercise Science and Sports Medicine: Exercise and the Female: A Lifespan Approach. Carmel, Calif:Cooper Publishing Group; 1996:413-451.
  13. Clapp JF III, Simonian S, Lopez B, Appleby-Wineberg S, Harcar-Sevcik R. The one-year morphometric and neurodevelopmental outcome of the offspring of women who continued to exercise regularly throughout pregnancy. Am J Obstet Gynecol. 1998;178(3):594-599.
  14. Clapp JR III. Morphometric and neurodevelopmental outcome at age five years of the offspring of women who continued to exercise regularly thought-out pregnancy. J Pediatr. 1996:129(6):856-867.
  15. Clapp JF III, Kim H, Burciu, Schmidt S, Petry K, Lopez B. Continuing regular exercise during pregnancy: effect of exercise volume on fetoplacental growth. Am J Obstet Gynecol. 2002;186(1)142-147.
  16. Magann EF, Evans SF, Weitz B, Newnham J. Antepartum, intrapartum, and neonatal significance of exercise on healthy low-risk pregnant working women. Obstet Gynecol. 2002:99(3):466-472.
  17. Clapp JF III: The course of labor after endurance exercise during pregnancy. Am J Obstet Gynecol. 1990;163(6 pt 1):163:199.
  18. Clapp JF III, Little KD: The interaction between regular exercise and selected aspects of women’s health. Am J Obstet Gynecol. 1995;173(1):2-9.
  19. Clapp JF III, Capeless EI. Neonatal morphometrics after endurance exercise during pregnancy. Am J Obstet Gynecol. 1990;163(6 pt 1):1805-1811.
  20. Cunningham FG, et al. Williams Obstetrics (20th ed.) Stamford, Conn: Appelton and Lange; 1997;240.
  21. Clapp JF III. Exercise during pregnancy: a clinical update. Clin Sports Med. 2000;19(2)273-286.

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