Exercise, Even Late in Pregnancy, Seems
NEW YORK, Mar 20 (Reuters Health) - Regular
exercise during pregnancy can help women and their newborns, but
the particulars of this benefit depend on the intensity and
timing of the exercise regimen, study findings suggest.
Previous studies have shown that, in general,
women who exercise throughout their pregnancies have larger
placentas than their more sedentary peers but that a more
intense exercise regimen may result in babies who weigh less at
The volume of the placenta is a general
marker of the structure's ability to transport oxygen and
nutrients to the fetus, Dr. James F. Clapp III, lead author of
the current study, explained in an interview with Reuters
In their study, Clapp and colleagues found
that women who exercised at the same rate throughout their
pregnancy, or boosted the intensity of their exercise regimen
later in pregnancy, gave birth to infants who were lighter and
had less body fat than women who slowed down in the final
However, none of the babies born to women who
exercised moderately or intensely through the ninth month were
considered low birth weight, according to the report published
in a recent issue of the American Journal of Obstetrics and
Gynecology. Low birth weight is associated with developmental
problems in childhood and may be linked to heart disease and
other health problems later in life.
The findings indicate "that regular
weight-bearing exercise is beneficial for both mother and baby
and that the amount of benefit varies with the timing and amount
of exercise," Clapp told Reuters Health. "If the woman
is healthy and the pregnancy normal, regular exercise can do
nothing but improve the situation."
Clapp and colleagues from Case Western
Reserve University in Cleveland, Ohio assigned 75 women who
exercised regularly to one of three aerobic exercise programs
during their eighth week of pregnancy. Women worked out on a
treadmill, took step aerobics or used a stair-stepping machine.
Women in the "Lo-Hi" group did 20
minutes of aerobic exercise 5 days a week and increased the
duration to 60 minutes by the 24th week of pregnancy until their
delivery. Women in the "Hi-Lo" group exercised for 60
minutes 5 days a week through week 20 and then decreased the
duration to 20 minutes from week 24 until the end of the
In the third group, women exercised for 40
minutes 5 days a week throughout their pregnancy.
Infants of women who exercised intensely in
the middle or late stages of pregnancy were significantly
lighter and had less body fat than infants born to the moderate
exercisers, although none of the infants were small enough to be
at risk for medical or developmental problems.
Women who exercised vigorously early on and
then reduced the intensity of their program as they approached
their due dates weighed more and had heavier placentas than
women in the other groups. While a heavier placenta can be
protective in some cases, the heavy exercisers did not have
dangerously light placentas, Clapp said.
He suggests that future studies investigate
the use of exercise as a way to prevent complications in certain
individuals, including women at risk of delivering premature and
low birth weight babies, as well as the effects of different
types of workouts such as scuba diving and spinning.
Journal of Obstetrics and Gynecology 2002;186:142-147.
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