By Dr. Thomas deHoop / Kalispell OB/GYN

Q:

I am a runner in the first trimester of my pregnancy. Is it safe for me to continue to exercise in pregnancy or should I stop or significantly modify my activity until after I deliver?

 A:

That is a great and often asked question. Now, more than ever, women are reaping the benefits of regular exercise. For many women, physical fitness and active recreation is a way of life, so when a woman becomes pregnant and wants to continue her routine of daily exercise, is it possible? Is it safe? Is it recommended? What are the risks of exercise in pregnancy? What are the benefits? What types of exercise are allowed and what complications of pregnancy preclude exercise of any kind?

 

The majority of women who desire to continue their exercise routine during pregnancy are motivated by the desire to maintain health benefits of muscular and cardiovascular fitness. For most healthy women with an uncomplicated pregnancy who engage in a moderate level of physical activity before pregnancy, fitness can be maintained throughout pregnancy and in the postpartum period. The goal of exercise in pregnancy should always be to maintain a sense of well-being and fitness, not to curb weight gain, maintain a certain level of fitness or competitively train. Those women who are interested in maintaining performance need closer follow-up with their healthcare providers.

 

How intensely can I exercise?

Studies of exercise in pregnancy showed no effects on fetal heart rate when mother’s heart rate was kept below 70% of their maximum heart rate. Mothers with a heart rate above 70% (the anaerobic range) had transient decreases in fetal heart rate during the recovery period, but no long-term effects were discovered. Based on these findings, a “submaximal threshold” level of exercise is recommended. If one knows their maximum heart rate from prior exercise testing, then 70% of that is the submaximal threshold. Other methods to determine maximum heart rate include, estimating it using the age-based formula of 220 minus your age equals your estimated maximum heart rate. Lastly, you can rate your perceived exertion on a scale of 0 to 10 where 10 is your maximum exertion. Your perceived exertion during exercise is recommended to be at or below 7 on a scale of 0-10.

 

What changes occur as the pregnancy advances that affect my exercise?

Your center of gravity shifts as the baby grows and has several effects: you may experience more back strain as the baby grows that can cause more hip, back and sciatic nerve pain. This may be improved by stretching or back strengthening exercises or worsens with certain types of exercise. The shift in your center of gravity will also affect your balance and could increase the incidence of falls with some exercises and should be undertaken carefully. The changes in pregnancy cause more joint laxity and any fall could result in serious injury to you or your baby. Although direct trauma to the baby from a fall is rare, a fall can lead to premature separation of the placenta, called an abruption, which is an emergency for the mother and baby and could lead to the need for an early and premature delivery.

 

As your baby grows, your uterus enlarges, and when you lie on your back it can compress the large vessel (the vena cave) that brings blood back to your heart. This can decrease your cardiac output, which can decrease oxygen-rich blood flow to you and your baby. As a result, during times of increased cardiac need, like when you are exercising, you should not lie flat on your back. If you do lie down, you should shift your weight to your left hip by slightly elevating your right hip with a rolled up towel to help shift the weight of the uterus off the vena cava and improve blood flow back to the heart. Lastly it is important to drink plenty of fluids when exercising to prevent dehydration. You may need to alter your routine or exercise regimen to accommodate these changes.

 

What are the effects on the baby?

Concerns in the past regarding exercise in pregnancy with regard to miscarriage rates, fetal growth, and premature labor have prompted multiple research studies over the past several decades. Theses studies have concluded that these concerns are unfounded in otherwise healthy women with low risk pregnancies. Women who participated in moderate amounts of exercise in early pregnancy, had the same rate of miscarriages as those who did not. Furthermore, the rates of premature labor and premature delivery were the same between groups. Multiple studies on fetal growth were unable to draw clear conclusions regarding differences in birth weight, but none showed significant fetal growth restriction. There are some data that report infant APGAR scores (the 1 -10 score a baby gets at birth assessing health at delivery) are higher in babies when the mother participated in regular exercise. The hope that women who exercised would have shorter labors or easier labors was unfortunately found to be false. Studies have shown that women who exercise during pregnancy also suffer fewer adverse symptoms of pregnancy such as anxiety, insomnia, and lowered self-image than those who didn’t exercise.

 

What kinds of exercise are allowed in pregnancy?

A woman can continue in either weight-bearing (running, walking, dancing or step aerobics) or non-weight-bearing (swimming or spinning) aerobics, although non-weight-bearing exercise will minimize the risk of injury and increase the likely continuation of exercise during pregnancy. Studies have shown that women who participate in non-weight-bearing exercise were more likely to continue with the same level of satisfaction throughout their pregnancy as compared to those who participated in weight-bearing exercise. As previously mentioned, activities where a sharp sense of balance is needed and the likelihood of falls significant, should be substituted for other, less risky activities.

 

What should I do if I plan to exercise regularly in pregnancy?

If you are already exercising regularly, discuss with your caregiver to ensure you don’t have conditions related to pregnancy for which exercise is contraindicated: pregnancy associated hypertension, preterm labor, and premature rupture of membranes or incompetent cervix. You should discuss your exercise plans and make sure your goals are reasonable, attainable and safe. If you haven’t been exercising, in addition to talking to your caregiver about your ability to begin exercise, you should consider starting a program with a certified trainer with specific expertise in exercise in pregnancy. Even if you start a low-impact activity like walking, you stand to improve your health and sense of wellbeing.

Most women who currently exercise and those who would like to start during their pregnancy should have no trouble doing so with the right supervision. The primary goal of exercise is to promote health and a feeling of wellbeing in pregnancy and this does not change with pregnancy.

 :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

Dr. deHoop is a regular contributor to 406 Woman Magazine.  Dr. deHoop has been writing, publishing and lecturing about the female athlete for almost two decades.

This article  appears in the  February/March 2014 addition online and in print version around the Flathead Valley.

PLEASE NOTE: This information is not intended to be medical advice.  It is general health information and does not take into account your particular health status nor is it a substitute for personal medical care.  Kalispell OB/GYN shall not be liable for any damages arising out of the use of the content herein.