Warning Exercise and Pregnancy is Best Not Bed Rest

wellness Dec 13, 2021
Warning Exercise and Pregnancy is Best Not Bed Rest

You think you are having a hard time lifting today.  Try lifting with another 20-30 lb person inside of you!  Every day, women are performing feats of strength and fitness while pregnant.  As healthcare providers, we are afraid of pregnant women and often place limitations on them.  Recent changes in the literature suggest that MOVEMENT and NOT bed rest are the way to go for these extraordinary women.  This week at Maximal Being, we discuss exercise and pregnancy



An Exercise and Pregnancy Primer, A Healthcare Story Of Mine

It is 2 am, and the pager goes off.  I return the call, and it is a 24-year-old woman in her third trimester of pregnancy, in the emergency department sick!  She is yellow from jaundice and in pain.  She has a fever and is unstable with low blood pressure.  

The Emergency Department did an ultrasound, and there is a stone in her bile tube, blocking the way.  She has a bloodstream infection from this stone, and it is my job to come in and get it out!  However, I have to use X-rays to do this.  

At 2 am, you realize that two lives are at stake.  When it comes to cholangitis (bile duct infection), you have to move fast! 

 I booked OR time and talked to Anesthesia, who had concerns about the X-ray exposure.  Fortunately, reviewing the literature (via my wonderful wife, a Board-Certified OB-Gyn), I knew that this risk was minimal and that we had to save these two humans lives!  The Anesthetist agreed that we got the patient on the table; I performed a procedure to clean out the bile duct and place a stent.  Rapidly the blood pressure returned to normal, and both mom and baby were well.


Healthcare Providers are Afraid of Pregnant People

This story is not to brag about my performance as a Doc, but rather to demonstrate how healthcare providers are afraid to manage pregnant people.  We treat them with a degree of caution that is warranted but often place limitations that are not needed.

Primarily these limitations are since two people are involved in each case.  Physiology is different during pregnancy, and there is a lack of research.  The fact that there is a local pool of data in pregnant patients is mostly ethical.  For example, giving an experimental drug to pregnant women can cause issues with the mother and the fetus.


exercise and pregnancy physiology


With that said, the classical recommendations for exercise and pregnancy are that of limitation up until recently.  As healthcare providers, rather than mobilizing our women warriors, we place them on bedrest.  I will tell you that the rules have changed recently due to quality clinical research.  Having more research to back these concepts, there is a movement toward proving the beneficial effects of exercise and pregnancy.


Physiologic Changes During Pregnancy

Before we discuss exercise and pregnancy, let’s talk about how regular physiology changes during pregnancy.

During pregnancy, physiology changes to lend some advantages and some limitations to exercise and pregnancy.  Below is a summary of these changes.

  • Increased cardiac output = blood pumping to organs 2.5 L/min > 5 L/min, 6, and 7 with each trimester
  • Stroke volume and HR up (15bpm)
  • More fluid circulating
  • Low Hemoglobin = high RBC but a higher volume of blood > swelling.
  • Higher volume of air per breath
  • More breaths per min
  • GI and GU tracts compressed so slower.
  • Skin changes – stretch marks typical, sweat glands produce higher.

Firstly, to work out, whether it be weightlifting, HIIT, or cardio, you need a working pump (the heart) to move oxygenated blood to your tissues and fuel your workouts.  During pregnancy, the amount of blood volume due rises, as does the ability for your heart to pump that blood (stroke volume), the speed of moving that blood (heart rate).  If you multiply these numbers, you get your cardiac output.  Therefore, the cardiac output rises from the non-pregnant 2-3 Liters per minute to 5 L/min during the first trimester, 6 L/min the second, and 7 L/min during the third!


The Impact of Pregnancy on your Red Blood Cells

As stated above, the blood volume is high, but so are the number of red blood cells.  Red cells deliver oxygen to your tissue and take carbon dioxide away from the tissue.  Your veins are the piping that moves blood away from the tissues.  An added limitation of pregnancy is that your uterus’s weight can push on your main vein pipe, the vena cava, and limit the emptying of blood from your tissue to your heart, especially when lying on your back.

Unfortunately, despite this superhuman response, the ratio of red cells to blood volume is lower during exercise and pregnancy.  This volume can lead to swelling (edema) and some limitations with training theoretically.

 Women also breathe faster during pregnancy, and on the other end, their guts and urinary tracts move slower due to hormones and physical space limitations from the uterus/baby.  Finally, skin and joints become laxer to allow the baby to fit in the pelvis (stretch marks) and through the pelvis during the birthing process.


Situations Where Exercise Limitations May Be Recommended During Pregnancy


when to limit exercise and pregnancy


Now that I have enlightened you all with these changes, perhaps you see why health care providers and trainers handle exercise and pregnancy with kid gloves.  There are certain medical conditions in which women are on bedrest or have limitations.


Conditions where exercise and pregnancy may be harmful

  • Certain types of heart and lung diseases
  • Cervical insufficiencyor cerclage
  • Being pregnant with twins or triplets (or more) with risk factors for pre-term labor
  • Placenta previaafter 26 weeks of pregnancy
  • Pre-term labor or ruptured membranes (your water has broken) during this pregnancy regular physical activity
  • Preeclampsiaor pregnancy-induced high blood pressure
  • Severe anemia

On the flip side, avoid certain types of exercise during pregnancy.


  • Contact sports and sports that put you at risk of getting hit in the abdomen, including ice hockey, boxing, MMA fighting, soccer, and basketball
  • Skydiving
  • Activities that may result in a fall, such as downhill snow skiing, water skiing, surfing, off-road cycling, gymnastics, and horseback riding
  • Hot yoga” or “hot Pilates,” which may cause you to become overheated
  • Scuba diving
  • Activities performed above 6,000 feet (if you do not already live at a high altitude

***Maybe lying supine (on your back)? You should avoid lying on your back due to the impaired return of deoxygenated blood from the tissue to your heart.


The New Perspective of Exercise on Pregnancy

Alright, now that we have reviewed the classical information regarding exercise and pregnancy, let’s go through what the new evidence says and what YOU CAN DO!  For s full account of these new guidelines, I recommend THIS resource and this infographic.


Activity Restriction is Not Safe for Pregnancy

When it comes to mom’s health and safety, it seems that restricting activity may NOT be best.  Women who move less during pregnancy are more prone to gestational diabetes (high blood sugar).  

Gestational diabetes (high blood sugar and insulin) will often lead to larger babies and growth and development issues.  One retrospective study showed that the risk of gestational diabetes without exercise during pregnancy increased by 4% for each day of inactivity.  


Protect your Bones with Exercise and Pregnancy

Another consideration is bone loss.  As we know, weightlifting can lead to improvements in bone density and prevent resorption, termed osteoporosis and osteopenia.  Well, in this study, bone density decreased during prolonged inactivity during pregnancy.  Pregnancy places higher needs for calcium, but the rate of removing calcium from bone is higher.  So if you can counteract this (as in weightlifting), the evidence suggests benefit.


The Impact of Exercise on Blood Clots in Pregnancy

Pregnant women also carry a higher risk of blood clots when compared to non-pregnant people.  Likely this is due to hormonal input and the higher blood volume, with a lower return of blood to the heart leading to stasis in the venous system.  Blood clots can form and dislodge, leading to clots in the lung (pulmonary embolism) and the brain (stroke).


why bedrest is not good for pregnancy


There is the potential for disaster her with an already delicate balance between the cardiovascular and pulmonary changes with pregnancy.  Having clots in eh mix can lead to disaster for mom and the baby.  Exercising will circulate blood, prevent stasis, and clots.  Even just walking, standing, or any movement every 4-6 hours can help prevent clots.


Post-Partum Depression Risk Reduces with Exercise and Pregnancy

Not to be undervalued are the psychological impacts of exercise during pregnancy.  Pregnancy imparts changes in life, your body, careers, relationships, and freedom.  Hormonal inputs and postpartum depression are REAL!

 Women at a higher risk of postpartum depression are often also more likely to be placed on bed rest.  On the other hand, bed rest can also lead to higher risks of postpartum depression.  Any movement and outdoor exposure can certainly limit or mitigate these risks, as discussed in this study.


The Impact of Exercise and Pregnancy

What about exercise.  Well, regarding mood, a study done in 2014 by O’Connor et al. demonstrated that supervised, low-moderate intensity strength training could be safe and effective for pregnant women.  


exercise and pregnancy that are safe


Furthermore, in 2017 Ward-Ritacco, et al. evaluated a similar strengthening program.  This study demonstrated improved feelings of energy and fatigue.


High-Intensity Interval Training, CrossFit™, and Well-Conditioned Pregnant Athletes

 For some of you out there, this low/moderate intensity isn’t enough.  So, the question arises, is it safe for mothers to do higher intensity training like high-intensity interval training (HIIT) and CrossFit™ style exercises.  In 2015 Kehler, et al. studies female athletes that became pregnant and were already well-conditioned.  These athletes were able to maintain this level of intensity throughout their pregnancy safely.   

Similarly, you can do HIIT throughout pregnancy.  Hinman, in 2015, evaluated this concept.  This trial concluded that moderate- and high-intensity exercise in normal pregnancies is safe for the developing fetus and has several significant benefits. Thus, the practice should be encouraged according to the woman’s preconception physical activity level.

Next, let’s talk about how training can impact the baby! 


The Impact of Exercise and Pregnancy for Preventing Pre-Term Birth

A primary concern amongst pregnant people is pre-term birth.  Yes, miracles occur all the time, but this is the ideal situation if you can avoid pre-term labor.  There are two randomized trials of women who were at high risk for pre-term delivery (above). 


impact of the baby exercise and pregnancy


Both trials showed that activity restriction did not prevent pre-term labor.  A secondary analysis of the Maternal-Fetal Medicine (MFM) Pre-term prediction study showed that activity restriction led to two times more pre-term births than the non-activity restricted counterparts.

A small pilot study showed an inverse relationship between the number of steps per day during pregnancy and pre-term labor. 


Multiple Babies, Small Babies, Premature Rupture, Exercise May, Protect You and Your Baby

The next thing to discuss is other high-risk women.  Such as those with premature rupture of the membranes (PROM), high blood pressure, small babies (FGR), and multiple babies.  A Cochrane review (a fantastic review of 12 randomized trials) strict bed rest showed no benefit both to the mother and the baby for numerous babies.  

Another review of one randomized trial showed that for FGR, there were no benefits of bed rest. Specifically, there are no differences in infant birth weight, Apgar scores, cord pH, or operative delivery rate.


High Blood Sugar, Exercise, and Pregnancy May Help

Finally, what about gestational diabetes, or high blood sugars from just being pregnant.  We care about gestational diabetes because this can significantly impact the health of the baby.  Namely, elevated insulin levels can cause the baby and mother to store fat, leading to large babies.  Large babies, as well as small babies (FGR), can have issues with development and also cause damage during vaginal births, and have high c-section rates.

Exercise to the rescue again.  A review from Spain of several trials showed that exercise during pregnancy could reduce unintentional weight gain and lower the risk of gestational diabetes for pregnant women.  This study also demonstrated benefit to the baby.  


Summary of Exercise and Pregnancy

Frankly speaking, exercise and pregnancy are a match made in heaven.  Debunk the old school thought process of strict bedrest.  Activity restriction does not appear to help women or their babies.  Exercise and pregnancy lead to improved outcomes for the woman’s health and her baby(s).  Any activity is better than none, but there is no need to dial it down if you are well-conditioned.  Follow the science, and you will succeed!

(that Your Doctor Won’t Tell You)

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