Exercise During Pregnancy

There are two main reasons for concern about exercising during pregnancy. One is that it may reduce the baby's oxygen supply, since exercise, like other sources of stress, reduces blood flow to the uterus. Another risk is overheating. As we have already seen, fetal development is highly sensitive to temperature, and elevations of more than 2^0 C (or above 1020F) can increase the risk of miscarriage and affect the formation of the brain and eyes.

Despite these theoretical concerns, there is little evidence that mothers who exercise or are physically very active have any particular problems with their pregnancies. Most studies have found no difference in prematurity or Apgar scores (measures of newborn health taken one and five minutes after birth) between babies born to mothers who exercise and those who are more sedentary. With regard to birth weight, there are conflicting reports about the effects of exercise; some studies have found that women who exercise have significantly smaller babies, but several recent studies refute these findings, and one actually found that the more women exercised, the larger their babies tended to be. The key factor here appears to be the amount of weight the mother gains. If exercise prevents the mother from gaining adequately. she is likelier to give birth to a low-weight baby, but women who exercise and gain sufficient weight do not appear to compromise their baby's brain and bodily development.

Offsetting its potential harm are the numerous benefits of exercise, many of which can be traced to the fact that it elevates a mother's levels of betaendorphin—-a morphine-like substance produced by the body that blocks the transmission of painful stimuli to the brain. In addition, exercise actually lowers the level of another stress hormone, Cortisol, in pregnant women. These hormonal changes explain why exercise often counteracts the emotional impact of other sources of stress. Exercise generally increases a woman's sense of well-being, and based on what we know about anxiety and stress, this is likely to have a positive influence on the fetus.

The best-documented benefit of exercise comes in labor and delivery. Women who exercise regularly fare much better during childbirth compared with women who do not. They perceive it to be less painful, and indeed it may be; one study found that women who exercise spend just twenty-seven minutes in the second stage of labor—pushing—compared with fifty-nine minutes for women who did not exercise during pregnancy. Shorter labor is generally beneficial to the baby, since it reduces the risk of complications. including oxygen deprivation of the brain.

Doctors have traditionally been rather conservative about exercise during pregnancy, but current evidence indicates that it is safe for most women, especially those who were already physically fit before conceiving. Exercise should be kept to a "moderate" level, meaning that it does not elevate the woman's heart rate above 70 percent of its maximum rate (220 beats per minute minus one's age in years)—for example, 133 beats per minute in a thirty-year-old. Because there is evidence that a woman's oxygen reserves are lower in the third trimester, it is a good idea to scale down exercise, particularly weight-bearing types, toward the end of pregnancy, as most women are lined to do anyway. Other situations to avoid include: (1) exercising at high altitudes (more than 10,000 feet), because the placenta is already having to compensate for lower oxygen levels; (2) exercising in hot weather. because of the risk of overheating the fetus; and (3) scuba and snorkel diving, because of the potential risk of accumulating excess nitrogen and other gases in fetal tissues. But other water immersion sports, like swimming and "aqua-jogging," are among the best forms of exercise for pregnant women. because the water helps dissipate excess heat from the mother's body.


There are some concerns about the mother exercising during pregnancy, but the benefits appear to outweight the potential deleterious effects and have no apparent effect on the child's IQ.

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 What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life
Books, Brochures, and Chapters>Book:  Eliot , Lise (2000-10-03), What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life, Bantam, Retrieved on 2011-07-18
Folksonomies: parenting babies development infants physiology


01 JAN 2010

 Baby Care Memes

A collection of memes to help me keep track of what behaviors to emulate and avoid during and after pregnancy.