ASRM
BULLETIN (reprint)
Volume 14, Number 18
March 16, 2012
Study Shows Moderate
Exercise May Help Normal Weight Women Get Pregnant Faster, While Vigorous
Exercise Delays Pregnancy for All But the Overweight or Obese
Danish and US researchers
found evidence for a relationship between increasing levels of vigorous
exercise and longer times to conception in healthy, normal weight women who are
planning to become pregnant. In overweight and obese women planning pregnancy,
however, vigorous physical activity did not result in delays.
Moderate levels of physical
activity were observed to result in small decreases in time to pregnancy
regardless of women’s BMI.
The observational prospective
cohort study used the internet to recruit and administer questionnaires to 3628
women, age 18 to 40. Participants accepted into the study were required to be
in stable relationships with male partners, planning to become pregnant, and
not receiving any fertility treatments.
The women were given baseline
questionnaires to gather information on their demographics, height, weight,
reproductive and medical history, lifestyle, and behavior. Follow-up
questionnaires were emailed to participants every two months for 12 months or
until the participant became pregnant. Eighty-three percent, or 3,027,
completed the study.
One of the things the women
were asked at baseline was the average number of hours per week they exercised.
In addition, they were asked to report different types of moderate and vigorous
activity separately. Activities such as running, fast cycling, aerobics,
gymnastics, and swimming were characterized as vigorous. Brisk walking,
leisurely cycling, golfing and gardening were considered moderate. Assigning
values- total metabolic equivalents (METs)- to the activities, the researchers
quantified the amount of moderate and vigorous physical activity each
participant engaged in.
The participants were
categorized by their exercise exposure and the results were further stratified
by BMI to see whether the effect of physical activity on time to pregnancy
differs according to body weight.
The researchers found that
there was an inverse association between vigorous physical activity and how
long it took to become pregnant for normal weight women (BMI under 25). In
overweight or obese women (BMI of 25 or above) there was no association between
vigorous exercise and a longer time to pregnancy.
Moderate physical activity
was associated with improved time to pregnancy across the range of BMI. Women
who engaged in 20-39 MET hours per week of physical activity had the shortest
times to pregnancy.
ASRM President-Elect, Linda
Giudice, MD, PhD, noted, “This study is particularly interesting because its
participants were recruited from the general population, not from infertility
patients. It points out the benefits of moderate exercise to all women who are
planning a pregnancy and suggests that women might reduce their time to
pregnancy by modulating their exercise programs.”
Wise et al, A
prospective cohort study of physical activity and time-to-pregnancy, Fertility
and Sterility in press.
