Welcome to womenspecific.com, the internet’s latest and most innovative website for female athletes of all ages and abilities. When I was invited to write the premier article for this great website, I jumped at the chance to educate women (and hopefully some men as well) about the effects of exercise in pregnancy. This topic has become near and dear to my heart as I have developed a particular liking to the “runner’s high.” I attended medical school and residency in the Rocky Mountain West, an area where people are particularly active and athletic. Why was it, then, that the concept of exercise in pregnancy was never addressed during my training? Was it because we were too busy learning about disease processes to think about PREVENTING disease? Was it because we were too sleep-deprived to think about cramming any more information into our exhausted brains?

As a medium distance runner and overtired student/resident, I never gave much thought to exercise in pregnancy. I was married during my third year of residency to a naval officer stationed 1000 miles away. I hardly had time to have sex, much less get pregnant. During my chief residency year, I had a little more time and I attempted to get pregnant without success. I wasn’t ovulating regularly and some of my colleagues and professors intimated that the cause was my “excessive running.” Hmmm… maybe the 100-hour work week had something to do with it?

After residency, I moved to Jackson, Wyoming and joined a progressive practice comprising two physicians and two nurse-midwives. Jackson is a town of extremes: extreme low winter temperatures, extreme real estate prices, extreme athleticism. With the help of fertility medication, I achieved a pregnancy. Then, I watched the numbers on the scale slowly escalate. I exercised minimally, gained forty pounds, and lied to my partners about my weight gain. I delivered my first daughter after 19 hours of labor. I stopped by the pharmacy on my way home from the hospital, and someone asked me when I was due. At that point, I decided to run a half-marathon when my daughter was one, then a full marathon during her second year of life. I needed the goal, otherwise, I was never going to lose the majority of that forty pounds.

The goal was accomplished, thanks to the help a very supportive husband and great babysitters, plus my running buddies. I became entrenched in the Jackson mentality of activity. I finished my second marathon in 2001, then became pregnant again without needing medication. This was a perfect opportunity to test the exercise in pregnancy theory. I could use myself as the experiment, with my old self as the control. I ran 15-20 miles per week until 26 weeks gestation, worked out with personal trainers every week and alpine skied until 24 weeks gestation. My last workout was three days before I delivered. The second go-around, I had a five hour labor, then was back running, albeit two miles, on postpartum day 12 with a total weight gain of 26 pounds. My obstetrical practice then changed forever.

Of course, obstetrical providers cannot base their practice patterns solely on personal experience. However, if I could achieve a fit pregnancy then why couldn’t my patients, many of whom are elite athletes? I began researching exercise in pregnancy and based my recommendations on that data as well as my own experience. Below, you will find an overview of the historical recommendations of antenatal activity, a review of the current medical literature and recommendations for exercise in pregnancy and my so-called recipe for success. Keep in mind that there are complications of pregnancy that make exercise contraindicated and that each woman should consult her obstetrical provider prior to initiating or continuing an exercise regimen during pregnancy.

HISTORY
There wasn’t a lot of information about the effects of exercise in pregnancy until the late 1990’s. In the handbook Maternity without Suffering, published in 1902, the first recommendation in preparation for motherhood was exercise. Dr. Emma Drake, the author of the text, stated that “the work about the house is the best exercise a woman can take…. All the muscles are brought into play….” She recommended against heavy lifting, but felt that cooking, cleaning, gardening, and walking were the prescription to a healthy pregnancy and delivery. Per Dr. Drake, ”...Consult your physician as to the kind of exercise you need, and take it painstakingly, not with the thought that you are going to spare yourself pain, but that you are going to make yourself strong and give to your unborn child vigor and strength of mind and body.”¹

By the late 1940’s, exercise in pregnancy, especially walking, was felt to calm the nerves, promote sleep and increase appetite. However, it was felt at that time that heavy lifting caused miscarriage, and heavy exercise was discouraged as being too stressful for the mother. ² Pregnant women were cautioned never to exercise to the point of fatigue and never to run, play tennis, golf, swim, cycle, skate, dance or horseback ride. Again, the womanly duties of housework were never restricted.³ Then came the late 1950’s and 1960’s, the era of the 10 pound maternal wait gain during gestation, regardless of whether smoking was necessary to achieve that demand! Many times had my mother reminded me that she gained 10-11 pounds during her pregnancies with both my sister and me! The emphasis was definitely on remaining as thin as possible during gestation, but not necessarily exercising to control weight gain.

CURRENT RECOMMENDATIONS AND LITERATURE REVIEW—CAUTION: THERE IS A LOT OF SCIENCE IN THIS SECTION!

Current weight gain recommendations for pregnancy are 25-35 pounds for a normal weight woman. Most of the data on exercise in pregnancy comes from Canada, and a little from Europe, Australia, and the United States. In my review of the recent medical literature (2000-2005), I found approximately 200 articles pertaining to exercise in pregnancy. This pales in comparison to the thousands of articles regarding preterm labor and other pregnancy complications. Most of the studies have been performed by a few researchers who have made the study of exercise in pregnant women their lives’ work. The studies, from a statistical standpoint, are often inadequate because they study too few numbers of women, or their scientific methods are not accurately standardized.

HERE IS A BRIEF OVERVIEW OF WHAT I DISCOVERED:

The most recent literature demonstrates that exercise is not harmful to fetuses, and is beneficial to normal pregnant women. In fact, several studies have shown that exercise is beneficial even in pregnant women who begin their pregnancies with sedentary tendencies. The benefits can be broken into categories that encompass physical and mental well being. Studies have been performed in small numbers of women ranging from initiating exercise in sedentary women in early pregnancy, to maintaining high intensity levels of exercise in pregnant athletes. Women exercising at least three times per week at a target heart rate of 150-156 beats/minute were found to increase their aerobic fitness while maintaining similar levels of lactate concentrations throughout their pregnancies.⁴

In another review, maximal aerobic power was maintained in pregnancy, but anaerobic capacity was slightly decreased as gestation progressed. Because there is an increase in resting heart rate in pregnant women, plus a smaller heart rate reserve, these researchers describe the use of rate of perceived exertion.⁵ A survey of competitive female athletes corroborates the rate of perceived exertion theory. These women decreased their cardiovascular and resistance training in pregnancy, but were able to resume a postpartum training program without difficulty.⁶ A few women are able to maintain their elite athletic fitness levels in pregnancy, as evidenced in the women’s cycling events in the 2000 Olympic Games. The rest of us, well…we do the best we can. Of particular interest to me was an article looking at the effects of altitude on exercise during pregnancy. Although no real experimental data has been gathered, the hypothesis is that, at altitude, hemoglobin oxygen saturation falls. Uterine blood flow is lower in pregnant women at altitudes of 9000 feet versus 4800 feet. These two findings, coupled with the fact that most pregnant women develop a dilutional anemia (that is, blood volume increases more than red blood cell numbers), suggest that fetal oxygen delivery may be lower at altitudes higher than 4800 feet. Again, this is theory only and has never been proven.⁷

On the contrary, several studies have looked at the effects of maternal exercise on the fetus in utero, maternal labor and delivery, and neonatal outcomes. There have been documented fetal effects of aerobic activity, including temporary elevation in fetal heart rate, that have not resulted in fetal distress or injury.⁸ In early gestation, as the embryo’s organ systems are developing, elevated core body temperature can result in birth defects or miscarriage. Two studies have measured maternal body temperatures before, during and after exercise at up to 85% of age-adjusted maximum heart rate. Both showed an actual protective effect, in that pregnant women are able to dissipate heat more effectively than non-pregnant women.⁹, ¹⁰ Data on birth weight have been mixed, with some studies showing lower but not really relevant decreases in birth weight, while others found no difference at all or even an increase in birth weight. Obviously, the jury is still out on that topic until larger numbers of women can be observed. In women having their first child, the risk of cesarean delivery may be reduced in those participating in regular exercise,¹¹ but they may require more inductions of labor and longer labors than women not exercising.¹²

I see pregnant women every day. I have been a pregnant woman twice. Let’s face it—a lot of women don’t feel particularly attractive or have a great body image during pregnancy. Couple that with an inherent lack of sleep in the third trimester and postpartum, and some of us feel downright lousy! It’s worth it, though, to bring a cute little baby (or babies) home to live! Many studies demonstrate lower levels of physical complaints, anxiety, insomnia and depression in exercisers and a higher level of psychological well-being and body image satisfaction.¹³, ¹⁴ Those findings, in and of themselves, have me sold on encouraging physical activity before, during and after pregnancy.

Some of the data I found the most fascinating pertained to exercise in the prevention of pre-eclampsia (also known as toxemia of pregnancy). For women having a prior pregnancy complicated by pre-eclampsia (initially diagnosed by elevated blood pressure, presence of protein in the urine and facial/hand swelling) the incidence of pre-eclampsia in a subsequent pregnancy was up to 54% lower in women who exercised versus women who did not.¹⁵ The cause of pre-eclampsia is unknown and affects up to 7% of pregnancies. It accounts for about 15% of all preterm deliveries, and is a cause of low birth weight and even fetal death in utero. There are many theories as to why pre-eclampsia develops, from poor placental development to changes in the maternal immune system, to genetic risk. All of these theories result in possible pro-oxidant accumulation and damage to the maternal and fetal blood vessels. These changes can also result in severe maternal disease including seizures, stroke, difficulty breathing and rupture of the liver. It is a complication that affects every organ system in a pregnant woman. Clinicians theorize that exercise increases the defense to pro-oxidants in the body, reverses blood vessel damage, and increases blood flow/oxygen delivery to the fetus, thus helping to decrease the adverse effects of pre-eclampsia.¹⁶ Because women who are diagnosed with pre-eclampsia are often placed on bed-rest as a means of controlling their blood pressure, the studies look at beginning an exercise regimen early in pregnancy, thus closing the proverbial barn door before the horse is out.

Another problem in pregnancy that can be positively influenced with exercise is that of gestational diabetes. Gestational diabetes is simply that—diabetes that is confined to pregnancy. However, women with diabetes in pregnancy are prone to other complications stemming from their elevated blood sugars, including too much amniotic fluid, preterm labor, and LARGE babies. Plus, they are at risk for developing adult onset diabetes later in life. In women who perform aerobic exercise in pregnancy, both blood glucose and insulin levels are lower.¹⁷, ¹⁸, ¹⁹ Lower blood sugars tend to correlate with fewer complications from gestational diabetes. Likewise, women with diabetes who enter pregnancy also benefit greatly from exercise and improved glucose control. Often, women with gestational diabetes are overweight; thus, the benefit of lower weight gain in pregnancy is recognized as well.

PUTTING IT ALL TOGETHER—CURRENT RECOMMENDATIONS

Overall, the recommendations for exercise in pregnancy are becoming more prevalent and more liberal. The American College of Obstetricians and Gynecologists states that “a wide range of recreational activities appears to be safe in pregnancy.²⁰” The Society of Obstetricians and Gynecologists of Canada take that statement even further. They stress that all pregnant women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises, to maintain a good fitness level throughout pregnancy and to choose activities with the least risk of loss of balance or fetal trauma. They also formally educate patients that adverse outcomes are not increased with exercise and that breast milk is not affected by exercise postpartum. Also, they encourage initiation of pelvic floor exercises postpartum to decrease the risk of future urinary incontinence.²¹

So, what do I recommend to my patients? First and foremost, I do not feel that pregnancy is an illness, although there are definite physiologic changes that occur. I strongly encourage all of my low-risk and many of my high-risk pregnant patients to exercise at least four days per week and that they incorporate both cardiovascular and strength training. I recommend that, in the first trimester, they keep their heart rates less than 160 beats per minute; in the second trimester, 150 beats per minute, and in the third, 140 beats per minute. I feel that is a safe margin for women to oxygenate their skeletal muscles while preserving uteroplacental blood flow, and thus, oxygen delivery to their fetus. I caution patients that the center of gravity changes as pregnancy progresses and that they should make concurrent changes in their activity and intensity as they see fit. I am a big believer in pelvic floor exercises (aka Kegel exercises). They have been shown to prevent pelvic prolapse and urinary incontinence later in life and have recently been demonstrated to facilitate pushing during labor and shorten the time necessary for pushing efforts.²², ²³ Use common sense—if you’re tired, stop and rest. Don’t do activities that you feel will put your baby or you at risk. I refrain from telling my patients which sports they can and cannot do, with the exception of scuba diving because it puts the fetus at risk for decompression illness, and contact sports for obvious reasons. I have patients who are professional skiers and mountain climbers. They dance, do pilates and yoga. They barrel race and work in hunting camps. They run marathons and do triathlons during pregnancy. They are happy and generally deliver healthy, normal weight babies at term, despite our altitude of 6500 feet. They also pass me in races when they are 36 weeks gestation, and I am not even pregnant! While I may be more liberal than other obstetrical providers, don’t get me wrong. If my patients have a condition or complication that prohibits exercise, I am as quick as anyone else to confine them to the couch.

When exercising in pregnancy, be sure to wear comfortable clothing and shoes with good support. Warm up for at least five minutes before initiating your workout. Make sure to stay well hydrated and eat enough calories to compensate for your workout plus an additional 300 calories daily as recommended in pregnancy. Remember that your center of gravity will change and that hormonal changes make your ligaments more lax and prone to injury. After 20 weeks, I recommend that upper body strength training be performed on a therapy ball. This engages the core muscles in the torso to tone them without straining the abdominal muscles, which can cause a separation between the rectus muscles. As long as no complications are incurred, I feel pregnant women can exercise to term, then renew an exercise regimen after delivery when bleeding subsides and they feel rested enough to resume activity. A word to the wise—after delivery, you may need a different workout bra, or may need to wear two!

Fitness regimens should be reviewed with your healthcare provider prior to their initiation or continuation in pregnancy, as there are conditions that necessitate little or no exercise. Women with bleeding, low placentas, threatened miscarriage, prior preterm labor or birth, or incompetent cervix may be restricted from exercise. Barring complications, both aerobic exercise and strength training are key to a fit pregnancy.

Maura Lofaro M.D., F.A.C.O.G
Jackson Hole Ob/Gyn, P.C.
Clinical Instructor, Department of Obstetrics and Gynecology, Univerity of Colorado Health Sciences Center

Edited: Kathy Watkins

REFERENCES

1. Drake, EFA. Maternity without Suffering 1902; Vir Publishing Company, Philadelphia.

2. Zabriskie L, Eastman N. Nurses Handbook of Obstetrics 1948; J.B. Lippincott Company, Philadelphia.

3. Fishbein M. Modern Home Medical Advisor 1935-1942; J.G. Ferguson and Associates, Chicago.

4. Marquez-Sterling S et al. Physical and psychological changes with vigorous exercise in sedentary primigravidae. Med Sci Sports Exerc 2000 Jan; 32(1):58-62.

5. Wolfe LA , Weissgerber TL. Clinical physiology of exercise in pregnancy: a literature review. J Obstet Gynaecol Can 2003 Jun; 25(6):473-83.

6. Beilock SL et al. Training patterns of athletes during pregnancy and postpartum. Res Q Exerc Sport 2001 Mar; 72(1):39-46.

7. Entin PL, Coffin L. Physiological basis for recommendations regarding exercise during pregnancy at high altitude. High Alt Med Biol 2004 Fall; 5(3):321-34.

8. Kagan KO, Kuhn U. Sports and pregnancy. Herz 2004 Jun; 29(4):426-34.

9. Lindqvist PG et al. Thermal response to submaximal exercise before, during, and after pregnancy: a longitudinal study. J Matern Fetal Neonatal Med 2003 Mar; 13(3):152-6.

10. Larsson L, Lindqvist PG. Low-impact exercise during pregnancy—a study of safety. Acta Obstet Gynecol Scand 2005 Jan; 84(1); 34-8.

11. Bungam TJ, et al. Exercise during pregnancy and type of delivery in nulliparae. J Obstet Gynecol Neonatal Nurs 2000 May-Jun; 29(3); 258-64.

12. Magann EF, et al. Antepartum, intrapartum, and neonatal significance of exercise on healthy low-risk pregnant working women. Obstet Gynecol 2002 Mar;99(3); 466-72.

13. Boscaglia N, et al. Changes in body image satisfaction during pregnancy: a comparison of high exercising and low exercising women. Aust N Z J Obstet Gynaecol 2003 Feb; 43(1):41-5.

14. Goodwin A, et al. Body image and psychological well-being in pregnancy: A comparison of exercisers and non-exercisers. Aust N Z J Obstet Gynaecol 2000 Nov; 40(4):442-7.

15. Sorensen TK, et al. Recreational physical activity during pregnancy and risk of preeclampsia. Hypertension 2003 Jun; 41(6):1273-80.

16. Weissgerber TL, et al. The Role of Regular Physical Activity in Preeclampsia Prevention. Med Sci Sports Exerc 2004; 36(12):2024-31.

17. Bessinger RC, et al. Substrate utilization and hormonal responses to moderate intensity exercise during pregnancy and after delivery. Am J Obstet Gynecol 2002 Apr; 186(4):757-64.

18. Wolfe LA, et al. Aerobic conditioning effects on substrate responses during graded cycling in pregnancy. Can J Physiol Pharmacol 2003 Jul; 81(7):696-703.

19. Avery MD, Walker, AJ. Acute effect of exercise on blood glucose and insulin levels in women with gestational diabetes. J Matern Fetal Med 2001 Feb; 10(1):52-8.

20. ACOG Committee Obstetric Practice. ACOG Committee Opinion. Number 267, January 2002: exercise during pregnancy and the postpartum period. Obstet Gynecol 2002; 99:171-3.

21. Davies GA, et al. SOGC Clinial Practice Obstetrics Committee, Canadian Society for Exercise Physiology Board of Directors. Exercise in pregnancy and the postpartum period. J Obstet Gynaecol Can 2003; 25:516-529.

22. Harvey MA. Pelvic floor exercises during and after pregnancy: a systematic review of their role in preventing pelvic floor dysfunction. J Obstet Gynaecol Can 2003 Jun; 25(6):487-98.

23. Waknine Y. Pelvic floor muscle training during pregnancy facilitates labor. BMJ 2004; 329:378-80.