For much of recent history, pregnant women have been treated as if they had an illness and were confined for fear that any physical activity would harm the fetus. Our understanding of pregnancy, exercise and health has come a long way. At the 2014 USA Track & Field National Championships, five-time 800-meter champion Alysia Montano competed when she was 34 weeks pregnant.
For the most part, running during pregnancy is safe and even beneficial, especially during the first two trimesters. Exercise during pregnancy has been associated with a reduced risk of developing certain obstetrical complications, including preeclampsia, pregnancy-induced hypertension and gestational diabetes. It's also associated with better tolerance of labor and a lower risk of C-section childbirth.
Frequent complaints of pregnancy, including nausea, heartburn, insomnia, varicose veins and leg cramps are reduced in women who remain active during their pregnancy. Other common discomforts of pregnancy, including fatigue, back pain, swelling of the extremities and shortness of breath are also lessened.
Despite the liberalization of medical guidleines for running during prgnancy, there are certain medical conditions that can be pre-existing or develop during pregnancy that would prohibit you from running while pregnant, including heart and lung disease, persistent bleeding in the second and third trimesters and ruptured membranes. Several other conditions require careful evaluation of the risks and benefits before continuing with your running program, including severe anemia, being extremely underweight, uncontrolled thyroid disease and inappropriate fetal size and development.
When running while pregnant, always be aware of warning signs, including vaginal bleeding, breathlessness at rest or out of proportion to the effort, dizziness, headaches, chest pain, racing heart rate, muscle weakness, significant swelling in feet or legs, uterine contractions that occur more than 30 minutes after running, decreased fetal movement, pelvic, hip, or back pain, chronic fatigue and leakage of fluids.
Here are guidleines for running through each trimester.
Although you might not look pregnant during the first trimester, most women certainly feel pregnant. Shortly after conception, hormone levels change and your body and uterus adapt to support the growth of the placenta and developing fetus. These changes result in the symptoms that many women experience in the first trimester, including fatigue, morning sickness and headaches.
Cardiovascular changes, including an increase in maternal blood volume and resting heart rate and stroke volume, occur early in the first trimester. This increase in maternal blood volume allows more oxygen and nutrients to be delivered to the fetus. Stroke volume begins to rise in the first 6 to 8 weeks of your pregnancy and increases as much as 10 percent by the end of the first trimester. Resting heart rate increases by 10 to 15 beats per minute.
Since fetal size and therefore its oxygen and nutrient needs are small in the first trimester relative to the other trimesters, increases in cardiac output create a circulatory reserve, which is why most women can tolerate running in the first trimester. Some women feel even better running in the first trimester than prior to pregnancy.
Base your intensity on effort rather than pace. The pregnancy-induced symptoms in the first semester, including nausea, vomiting and fatigue, may require you to adjust your training. If you experience morning sickness, decrease your training by 5 to 10 percent and run at a different time of day.