Overview
Gone are the days when doctors recommended rest during pregnancy. Now, the American Congress of Obstetricians and Gynecologists (ACOG) states that, “Becoming active and exercising at least 30 minutes on most, if not all, days of the week can benefit your health.” In fact, exercise may help alleviate backaches, constipation, bloating and swelling. In the past, doctors recommended limiting your heart rate to 120 beats per minute. Now, exercise guidelines are much more lenient.
What is Heart Rate?
Heart rate is simply the number of times your heart beats per minute. At rest, the heart should beat more slowly. As you begin to move, heart rate should increase the more you stress your body. The National Academy of Sports Medicine recommends healthy individuals exercise at 65 percent to 85 percent of your maximum heart rate (maximum heart rate = 220 – your age). However, these recommendations are not accurate during pregnancy.
Resting Heart Rate in Pregnancy
Pregnancy places greater demands on the cardiovascular system. During pregnancy, the heart has to work progressively harder to pump blood throughout the body due to the increasing needs of the fetus and placenta. According to the American Council on Exercise’s “Pre- and Post-Natal Fitness, “Resting heart rate climbs by eight beats per minute in the early weeks of pregnancy and continues to increase to a high of 20 beats above normal by 32 weeks.”
Exercise’s Effect on Heart Rate During Pregnancy
It is much harder to predict heart rate during exercise in pregnancy than in women who are not pregnant. Although heart rate does increase as a pregnant woman exercises, how hard she is working to reach that heart rate will vary throughout her pregnancy. The American Council on Exercise’s “Pre- and Post-Natal Fitness” states, “The heart-rate response to exercise also changes throughout gestation; it increases early in pregnancy, then falls gradually but continually throughout the latter trimesters.” For these reasons, targeting a specific heart rate during pregnancy may mean working too hard or not hard enough.
Rate of Perceived Exertion
Due to the variable nature of heart rate during pregnancy, the safest way of rating work is to use a rating of perceived exertion (Borg Scale). This is a scale of one to 10, where one is “no effort” and 10 is “maximal exertion.” In pregnancy, it is recommended to stay in the middle of this range. The ACOG recommends trying to “exercise moderately so you don’t get tired quickly. If you are able to talk normally while exercising, your heart rate is at an acceptable level.”
ACOG Recommendations
Although the ACOG recommends 30 minutes of moderate exercise for pregnant women most days of the week, it is important to check with your doctor before starting an exercise program. For certain high-risk pregnancies, including those with high blood pressure, risk factors for pre-term birth, vaginal bleeding or premature rupture of membranes, exercise may be contraindicated. It is also important that after the first trimester, it is not recommended to lie flat on your back during exercise.
