Doc Talk: Get the Facts on Pregnancy and Exercise

We sat down with Dr. Iris Moore of Middlesex Obstetrical & Gynecological Associates to talk about common myths, safe activities, and overall approach to prenatal exercise. Dr. Moore has specific interest in prenatal exercise and completed her resident research project by implementing a survey and gathering information about exercise habits from postpartum women tailored to specific exercise by type, frequency and timing of pregnancy and how it related to delivery.

What types of exercise are safe during pregnancy?
Many types of aerobic and strength training exercises are safe. There is a specific benefit, especially with decreasing gestational weight gain to possibly decrease the risk of gestational diabetes and hypertension.

There are a lot of conflicting studies related to the risk of hypertension and preeclampsia and if it is or is not decreased. The exercises that are the safest are low impact activities like walking, swimming and running, especially if someone had been a runner before pregnancy. Cycling on the road or stationary cycling is completely safe to continue doing. Strength training is also very good.

Should exercise be modified based on trimester or intensity? 
In a word, no. Every person is capable of varying intensity or activity based on their previous exercise experience and it will always be different. It is easiest to tailor exercise to the individual person and the conversation they have with their ObGyn. For some women that consistently exercise in their regular lives, they may maintain that intensity throughout each trimester. However, they probably will notice on their own this intensity will decrease over time based on the physiological changes of pregnancy. Also, their center of gravity will change with this progression.

Exercise has been found to be most in the second half of pregnancy, so it's definitely most important to maintain exercise and the second half, regardless of the intensity is the same or not.

Are there certain types of exercise to avoid during pregnancy?
Yoga is great but hot yoga and anything that requires lying flat on your back or standing up for long periods of time should be avoided. This is because during pregnancy, temperature regulation is very important, and it is a process that is strongly dependent on hydration and environmental conditions.

Avoiding high heat environments and maintaining proper hydration is especially important during pregnancy and the physiological changes that occur over this time.

Is it okay to start exercising while pregnant if you were not very active beforehand?
Absolutely, it is a great idea to begin exercising with pregnancy. A lot of women do see pregnancy as a time to eat healthier and start to exercise. It is best to start slowly with maybe 15 to 20-minute intervals of activity, three to four days a week.

Based on how you are feeling with the three to four days a week, you can increase the duration of exercise to 30 minutes, if you're comfortable and then increase the amount of days per week. The recommended amount of exercise by the Centers for Disease Control and Prevention (CDC) for all pregnant women is 30 minutes a day, five days week, so at least 150 minutes a week.

Starting off slow and setting a goal and maintaining that 150 minutes of exercise weekly is what people should strive for and starting with those low impact exercises like walking, modified yoga or swimming rather than running.

If you are a very active person, what is the best approach to prenatal exercise?
If you are someone that is used to very vigorous activities, then you should be able to continue those activities. One should monitor signs and symptoms of fatigue and hypoglycemia especially for 45 minutes or more of intense exercise during pregnancy. This is because patients are more likely to experience hypoglycemia and dehydration.

It is important to maintain hydration and possibly caloric intake during exercise. Maintaining hydration during long periods of exercise is extremely important. If they are a person that is used to that level of exercise and are in tune with how they're feeling during that exercise as long as you are feeling okay, it’s perfectly fine to keep up with a higher level of intensity. But if you are starting to feel fatigued or muscle strain, you should stop and recognize that the physiological changes of pregnancy may impede your ability to maintain the intensity of exercise you were used to.

Are there types of exercise that assist with labor?
There are several studies out there looking at how prenatal exercise affects the length of labor but also looks at the type of delivery (vaginal birth versus c-section).

One study focused on patients who ran regularly prior to pregnancy or continued with high impact activity in pregnancy especially in the second half of pregnancy. This particular study found that these patients did have lower length of labor and, but also very importantly, they also noted that they had a lower incidence of operative vaginal deliveries or c-sections.

There were also several studies looking at that trend related to decreased length of the labor, also having better outcomes through vaginal delivery. It was proposed that decreased c-s and operative delivery rate was due to improved cardiac function of the fetus which resulted in less emergent deliveries for fetal distress. Fetal distress occurs when fetal oxygen supply is compromised during labor and may be demonstrated as late fetal heart rate decelerations (slowing down), decreased heart rate variability (inconsistency) or increased heart rate with decreased variability.

Previously studies have shown fetal adaptations in response to maternal aerobic exercise training (decreased heart rates and increased heart rate variability). A dose–response relationship was demonstrated, indicating that an increase in maternal exercise intensity and time spent participating in physical activity results in a greater fetal cardiovascular adaptation. If the mom becomes more physically fit, both the mother and the baby experience a cardiovascular benefit. 

The study also found a decreased incidence of fetal distress which is an emergency pregnancy, labor, and delivery complication in which a baby experiences oxygen deprivation, causing changes in the baby’s heart rate and decreased fetal movement.

Are there any warning signs to stop exercising or that women should talk about in their appointments?

Yes, one way that women can gauge themselves during activity is to think of their physical exertion on a scale of 6 to 20. A six would be sitting still and resting and 20 is the most exertion. Women should try to maintain a level of 13, 14 exertion during exercise and if they feel like they're going way above that, they should stop or slow down. Also, women should be able to hold a conversation during exercise and that's a good way to be sure they're not overexerting themselves.

If you start to notice a lot of stress on your joints because of the musculoskeletal changes that are involved with pregnancy hormones and as well as your center of gravity, you should back off on exercise or even stop if you start having shortness of breath.

If you're feeling very lightheaded or dizzy during exercise, or having vaginal bleeding, contractions, or a very strong abdominal pain should stop and be evaluated by their healthcare provider right away.

If there is anything that is causing discomfort or concern, it is always a good idea to talk to your provider about it.

Are there any myths about pregnancy and exercise? 
Historically, women were told that they are supposed to be very sedentary during pregnancy and that they need to stay off their feet as much as possible. This is not true and is detrimental to health. Now, many women don't feel that way anymore, but it's still is something that does come up and that's a conversation to have that physical activity is a benefit for the mom and baby and it is good to be active as long as it is talked through with your healthcare provider and agreed that exercise is a healthy and safe activity for you.

What are the most common questions or concerns from expectant mothers about prenatal exercise?
The most common concern is to make sure that it's safe to exercise during pregnancy. And the answer is yes! We also often talk about the different types of exercises that they can participate in.

After giving birth, how quickly can you jump into a fitness routine? 
Women who exercise during pregnancy will be able to start exercise sooner after pregnancy. This also depends on the mode of delivery. Having a c-section requires more recovery time and you want to be sure to talk with your healthcare provider before starting physical activity.

It is always good to start slow to see how you feel and if you feel okay, then you can increase your intensity.

Final thoughts on pregnancy and exercise
Patients should always be talking with their physician or healthcare provider before they start an exercise routine because while it is okay for most people, it's not safe for everyone.

Expectant moms with conditions including, but not limited to significant heart or lung disease, a history of an incompetent cervix, have experienced bleeding in the second or third trimester, a diagnosis of preeclampsia, gestational hypertension, severe anemia or are considered an at-risk or high-risk pregnancy may need to alter or abstain from certain activities.