Beth Warren Nutrition Blog

Current Mood: Fitness During Pregnancy

October 24, 2019

Pregnancy is a time where a woman cannot deny her inner warrior. An intense strength comes out, which she may not know she was capable of feeling. It’s a shame not to take advantage of the fierce power in an otherwise healthy pregnancy if it is out of fear. 

Speaking from multiple personal experiences with pregnancy, I noticed something off about the past recommendations in fitness while pregnant. Back during my first pregnancy, I was advised that my heart rate shouldn’t go past 140 beats per minute. It wasn’t based on my personal capabilities, but a generalization based on “population” with the recommendations at the time. I remember participating in exercise classes and working out towards women next to me who were not as active and I, who had always been vigorously active, kept having to stop. Not because of how I felt, but because of a number.

Fast forward to recently completing my 6th pregnancy (thanks to G-d!), and was happy to hear that current recommendations stated that you could perform the exercise you were used to, with some necessary modifications as you progress, and go with how you actually feel - no heartbeat monitoring necessary. Intuitively, this makes sense. And it worked! The ACOG says, “Although an upper level of safe exercise intensity has not been established, women who were regular exercisers before pregnancy and who have uncomplicated, healthy pregnancies should be able to engage in high-intensity exercise programs, such as jogging and aerobics, with no adverse effects.

I kept an active training intensity in boxing and strength regiment until the end of my pregnancy journey. The modifications felt natural to me as I increased in size and physically couldn’t do the moves as I used to.

Aside from the physical benefits (I gained 15lb less than my other 5 pregnancies), I feel much stronger post-partum and actually felt I was carrying my weight throughout the pregnancy versus the weight bearing me down painfully (until I past the 40 week mark when everything just hurts - OUCH!). And don’t be afraid, the ACOG continues to say, “Although physical activity and dehydration in pregnancy have been associated with a small increase in uterine contractions, there is only anecdotal evidence that even strenuous training causes preterm labor or delivery.”

Moral of the Story: Identify your goals. Trust your body. Listen to it. Act on what you feel. Train with experts. Consult with whom you trusted, an MD who aligns with your goals. Do You. A healthy baby is of course the most important thing, but so is a healthy Mommy. Don’t discount her.

Current exercise recommendations while pregnant are not much different than the general population. The American College of Obstetricians and Gynecologists (ACOG) recommends at least 150 minutes of moderate-intensity aerobic activity for healthy pregnant women, and agree that the benefits of exercise at this time greatly outweigh the risks. The benefits not only benefit mommy-to-be, but the post-partum one and baby as well.

The acute physiological responses to exercise (heart rate, cardiac output, stroke volume, etc.) are increased during pregnancy. If a woman does not have any medical contraindications, it is appropriate to monitor exercise intensity using the rate of perceived exertion. According to ACOG, “Minute ventilation increases up to 50 percent, primarily as a result of the increased tidal volume.” This makes it harder for pregnant women to reach an anaerobic threshold with less available oxygen. They also note that, “Aerobic training in pregnancy has been shown to increase aerobic capacity in normal weight and overweight pregnant women.”

In addition to respiratory changes, circulation and blood pressure also may respond by decreasing, in order to sustain mom and baby from a circulatory standpoint during pregnancy. This is why it is recommended that pregnant women avoid or modify any supine positions after week 16 of pregnancy. Also, the baby’s weight in this position can decrease venous return as well as cardiac output, resulting in hypotension.

In addition to the physiological changes a woman experiences during pregnancy, it’s crucial to recognize the anatomical changes as well, especially the shift in center of gravity as pregnancy progresses. Lordosis may result in increased joint and/or discomfort in other areas. Metabolic demands also increase by approximately 300 kilocalories per day. It’s helpful to work with our registered dietitians to ensure you are adequately fueling while pregnant, especially if working out.


ACSM’s Guidelines for Exercise Testing & Prescription: Contraindications for Exercising during Pregnancy


Severe anemia

Unevaluated maternal cardiac dysrythmia

Chronic bronchitis

Poorly controlled Type 1 diabetes mellitus

Extreme morbid obesity

Extreme underweight

History of extremely sedentary lifestyle

Intrauterine growth restriction in current pregnancy

Poorly controlled hypertension

Orthopedic limitations

Poorly controlled seizure disorder

Poorly controlled hyperthyroidism

Heavy smoker


Hemodynamically significant heart disease

Restrictive lung disease

Incompetent cervix/cerclage

Multiple gestation at risk for premature labor

Persistent second or third trimester bleeding

Placenta previa after 26 week of gestation

Premature labor during the current pregnancy

Ruptured membranes

Preeclampsia/pregnancy-induced hypertension

Here are some other recommendations:

Source: Physical Activity and Exercise During Pregnancy and the Postpartum Period

Number 650, December 2015(Replaces Committee Opinion Number 267, January 2002) (Reaffirmed 2019)


Regular physical activity in all phases of life, including pregnancy, promotes health benefits. Pregnancy is an ideal time for maintaining or adopting a healthy lifestyle and the American College of Obstetricians and Gynecologists makes the following recommendations:


Physical activity in pregnancy has minimal risks and has been shown to benefit most women, although some modification to exercise routines may be necessary because of normal anatomic and physiologic changes and fetal requirements.

A thorough clinical evaluation should be conducted before recommending an exercise program to ensure that a patient does not have a medical reason to avoid exercise.

Women with uncomplicated pregnancies should be encouraged to engage in aerobic and strength-conditioning exercises before, during, and after pregnancy.

Obstetrician–gynecologists and other obstetric care providers should carefully evaluate women with medical or obstetric complications before making recommendations on physical activity participation during pregnancy. Although frequently prescribed, bed rest is only rarely indicated and, in most cases, allowing ambulation should be considered.

Regular physical activity during pregnancy improves or maintains physical fitness, helps with weight management, reduces the risk of gestational diabetes in obese women, and enhances psychologic well-being.

Additional research is needed to study the effects of exercise on pregnancy-specific outcomes, and to clarify the most effective behavioral counseling methods and the optimal intensity and frequency of exercise. Similar work is needed to create an improved evidence base concerning the effects of occupational physical activity on maternal–fetal health.




The American College of Obstetricians and Gynecologists. Physical activity and exercise during pregnancy and the postpartum period. Committee Opinion No. 650. Obstet Gynecol. 2015; 126:e135-42. Available from:

American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription, 10th ed. Philadelphia (PA): Lippincott Williams & Wilkins; 2017, p. 195-202.





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