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Exercise and Pregnancy

Chris Davlantes, MD (A Second Opinion)

So, I’m starting to wonder if the City Gym slogan should be revised to say: “Be Fit.  Be Well.  Belong.  Be Pregnant.”  I’m not sure if you’ve noticed, but there are quite a few members at our gym who in various stages of their pregnancy, so I thought it might be appropriate for me to focus this month’s article on some of the “old wives’ tales” or myths surrounding physical activity and exercise during pregnancy.  There are actually some interesting facts relating to pregnancies in the United States, which I uncovered while preparing for this month’s installment, such as:

  • Almost 4 million babies are born in the United States each year, although the total fertility rate (estimate of the average number of births women have over their lifetime) has been declining regularly since 2007.
  • Women are waiting longer to have children. In 1970, the average age of a first-time mother was 21.  In 2013, it was 26.
  • Sunday is the slowest day for deliveries (which is great, because – even though I’ve delivered a handful of babies emergently in the ER or even the hospital parking lot – I teach SPINPower® classes on Sundays, and I’d prefer that it doesn’t happen during one of my classes!)

Physical activity and exercise during pregnancy has minimal risks and has been shown to benefit most women, although modifications may need to be made to certain exercise routines.  Women with uncomplicated pregnancies are encouraged to engage in aerobic and strength-conditioning exercises before, during, and after pregnancy, as it has been shown that it:

  • Improves or maintains physical fitness, strength, muscle tone, energy level, stamina, and endurance
  • Helps with weight management (although this is NOT the time to begin exercising for the first time with a goal of weight loss)
  • Reduces the risk of gestational diabetes, especially in obese women
  • Enhances psychologic well-being (improvement in mood, better sleep, and less post-partum depression)


There are some myths which some people have regarding exercise during pregnancy, which I thought I’d help to dispel:

Myth #1: “If you never exercised much before the pregnancy, now is not the best time to start.”

If you were highly active before the pregnancy, you should remain just as active during and after the pregnancy.  If you were not a “gym person” before, you can start slowly by just going for a brisk walk every day.

The American College of Obstetricians & Gynecologists (ACOG) recommends at least 20-30 minutes of moderate-intensity exercise daily.

Physical inactivity and excessive weight gain during pregnancy may lead to maternal obesity and pregnancy-related complications such as gestational diabetes, high blood pressure, and pre-eclampsia.

An obstetrician should be consulted first if you have a history of heart or lung disease, severe anemia, pre-eclampsia, pregnancy-induced high blood pressure, cervical problems, 2nd or 3rd trimester vaginal bleeding, pre-term labor with current or previous pregnancies, or if it is a multiple gestation pregnancy (e.g. twins, triplets, etc.)


Myth #2: “Exercise during pregnancy may cause a miscarriage.”

Although evidence is limited, some benefit to pregnancy outcomes has actually been shown, and there is certainly NO evidence of harm, when exercise is not contraindicated due to other medical conditions.

Stop & seek medical attention if you experience anything abnormal, such as severe abdominal or pelvic pain, uterine contractions, vaginal bleeding, leakage of fluid, or decreased fetal movement.

There are some things to AVOID during pregnancy, such as:

  • Exercises which call for lying flat on your back for a long time
  • Contact sports or activities which have a high risk of falling/injury
  • “Hot Yoga” or “Hot Pilates” or anything involving extreme heat/humidity
  • Any activity which involves extensive jumping, bouncing, etc.
  • Examples of SAFE physical activities during pregnancy:
  • Walking, jogging, or running
  • Swimming (probably the safest aerobic workout)
  • Stationary cycling (here’s my plug for SPINPower® again!)
  • Dance/Zumba or low-impact aerobics
  • Modified Yoga or Pilates
  • Stair-climbing
  • Strength training

Myth #3: “You shouldn’t let your target heart rate get over 130 BPM.”

  • Heart rate responses to exercise are different during pregnancy, and a more effective means of monitoring exercise intensity is the use of a Rate of Perceived Exertion (RPE) scale.
  • Using a 0-10 “Modified Borg Scale” with “0” being no exertion and “10” being maximal effort, one should remain in the aerobic zone and try not to exceed the “moderately hard” stage, which would be an RPE of about 5-6.
  • “Talk test”:  As long as a pregnant female is able to still carry on a conversation while exercising, she is likely not overexerting herself.
  • Aerobic training in pregnancy helps to increase aerobic capacity.
  • Ensure proper warm-up and cool-down with every workout.
  • Stop if you have any of the following symptoms:  dizziness, chest pain, shortness of breath, palpitations, etc.


Myth #4: “It’s not safe to do abdominal workouts during pregnancy.”

  • Weight gain and the shift in the center of gravity which occurs causes 60% of females to experience lower back pain during their pregnancy.
  • Strengthening the abdominal muscles and entire core (e.g. doing gentle squats and/or pelvic tilts) may minimize this risk, and it may even assist during the delivery.


Myth #5: “Running is not safe during pregnancy.”

  • ACOG and the National Society of Sports Medicine both agree that pregnant women who are accustomed to running can continue to run during pregnancy.
  • Don’t overdue it:  this is NOT the time to get your PR or qualify for the Boston Marathon!
  • If something doesn’t feel right, cut back & check with your doctor.


Myth #6: “Exercise deprives nutrients from the baby and can stunt growth.”

  • In general, the baby will get what it needs during the pregnancy.
  • High-intensity or prolonged exercise in excess of 45 minutes, however, can lead to maternal hypoglycemia, so ensure that you eating enough calories before exercising or limit the duration of your workout, if needed.
  • Eat smaller, more frequent meals to keep your blood sugar balanced.
  • Drink plenty of fluids to avoid dehydration.
  • Clinical studies have shown that women who exercise vigorously during the 3rd trimester were more likely to deliver infants weighing 200-400g less than controls, but there was NOT an increased risk of fetal growth restriction (So, basically, babies may have been born “leaner”, but their organs and head circumference were found to be normal.)
  • Regular aerobic exercise in lactating women has been shown to improve maternal cardiovascular fitness without affecting milk production, milk composition, or infant growth.


In summary, despite the fact that pregnancy is associated with many anatomic and physiologic changes in the body, exercise has minimal risks and has actually been shown to be beneficial in most cases.  Women with uncomplicated pregnancies should continue to engage in physical activities and exercise, if they had already been doing that on a regular basis.  For those that had not exercised regularly prior to their pregnancy, it is the perfect time to begin to “Be Fit, Be Well, and Belong!”