Cycling During Pregnancy: Yes or No?
When an active woman becomes pregnant, she has many decisions to make. Should she continue her current exercise or training program? How much exercise is too much? Should she reduce her training intensity? Can exercise hurt her baby?
While questions are multiplying, well-meaning but unsolicited advice can make an expectant mom even more insecure: "Maybe you should just rest and concentrate on growing a baby." "All that exercise can't be good for a developing fetus, can it?" "You exercise too much anyway; this is a good time to take a break from all that."
Those kinds of comments haunt the expectant mother's every pedal stroke. "What if I fall or crash?" may become a question that adds to the growing list of concerns. "I don't want to risk any falls, but I don't want to stay home lying on the couch. What should I do?"
A visit to the obstetrician early in pregnancy will likely make women aware of the danger of engaging in any activity that could result in mild abdominal trauma. Everyone wants the best for the mom and the unborn child. The question is: what is best?
One short answer is that healthy, pregnant women benefit from at least 30 minutes of moderate activity on most, if not all, days of the week, according to the American College of Sports Medicine (ACSM) and the American College of Obstetricians and Gynecologists (ACOG). General benefits can include more controlled weight gain, less fatigue, and possibly even shorter labor. This is especially true for women who were active prior to becoming pregnant.
Unfit pregnant women will also benefit from exercise during pregnancy, but they need to ease into a more active lifestyle. Women who are pregnant with multiple babies or women with high-risk pregnancies should consult with a doctor, as it could be recommended that they avoid exercise altogether.
Another answer for women specifically interested in riding a bike outdoors during pregnancy is to use some caution. Riding a bike with wide tires can provide greater stability, and just getting on and off the bike safely is easier without clipless pedals. When bicycling, women may feel less susceptible to collision if they avoid group rides and descents, instead sticking to wide bike paths and even terrain.
Recommended intensity levels during exercise are more difficult to pinpoint. It's obviously unethical to ask pregnant women to endure a nine-month study of the impact on the fetus of repeated exercise to exhaustion, but there are still many useful studies of exercise during pregnancy that can help define appropriate exertion.
Women That Have Done It
Many women have remained active right up to the day of delivery. Mary Jane Reoch, a world-class road racer who became pregnant at 35, pedaled from conception to delivery and raced a criterium during her fifth month. Although she was criticized for "hurting the baby," her doctors were supportive of her exercise program.
Mary Jane was active literally right up to the end: She actually rode her bike the 10 miles to the delivery room, where she gave birth to a healthy 7-pound, 12-ounce baby girl.
Blaine Bradley Limberg completed four triathlons, a biathlon, and a cross-country ski race before he was born. Blaine's mom, Barb, found out she was pregnant in the months just prior to the, a race including a 2.4-mile swim, 112 miles of cycling, and 26.2 miles of running.
After consulting her team of health care providers—including midwives, an obstetrician-gynecologist, and others who had information about exercise and pregnancy—she decided to go ahead with training and the race. She completed the event when she was three and a half months pregnant.

By Gale Bernhardt For Active.com

What About the Baby?
There are several benefits to the mother if she maintains an exercise program while she's pregnant, but what about the baby? Numerous studies have followed offspring of exercising mothers and have found the babies to be healthy, with normal growth and development.
In an interesting study conducted at the University of Vermont, head researcher James Clapp, MD, matched two groups of pregnant families for socioeconomic status, education, marital stability and body size. The fathers were also included in the body size data.
The two groups were matched for pre- and post-pregnancy exercise habits; both groups of mothers breast-fed, had similar child care arrangements, and had comparable parental weight change over time.
The only difference between the two groups was exercise during pregnancy. One group exercised "vigorously" by running, doing aerobics, cross-country skiing, or some combination of all three. They exercised at least 30 minutes three times per week throughout their pregnancies. The second group ceased all exercise except walking.
The researchers found that by age five, the children of the vigorous exercisers had less body fat than the children born to the walking group. The children born to the second group were called "a bit on the fat side." In addition, the vigorous exercisers' children scored significantly higher on the Wechsler test of general intelligence and coordination as well as on tests of oral language skills.
General Guidelines for Exercise During Pregnancy
Not everyone will be able to maintain a regular exercise program during pregnancy. Some exercise, however, is better than none. ACOG and ACSM revised the recommendations for pregnant women in 2002 to make them less restrictive.
ACOG now suggests that women use their rate of perceived exertion (RPE) as a guideline rather than limiting themselves to a specific heart rate: Generally speaking, if you can carry on a conversation while you exercise, your heart rate is in the right place. This equates to a RPE of 12 to 14, or 60 to 80 percent of aerobic capacity for most pregnant women, according to ACSM (2006).
This guideline may be overly conservative for well-trained athletes. It's important that every woman establish her personal guidelines in consultation with her medical professionals.