Patients frequently ask questions about exercise while attempting pregnancy and exercise during pregnancy. In addition to the many health benefits gained by exercise, research suggests that moderate physical activity improves time to pregnancy across the range of BMI even in women who do not struggle with infertility. Let’s start with a brief explanation of BMI and its relevance to fertility.
What We Know About BMI & Fertility
- Fertility is decreased in women who are very overweight and who are underweight as both conditions can interfere with normal ovulatory function.
- BMI ranges (if you do not know your own BMI, use this free BMI calculator):
- Normal: 19-24
- Overweight: 25-29
- Obese: >30
- Women with a BMI > 29 and < 18 should see a doctor for a thorough evaluation of hormonal status related to ovulation.
- Women with a BMI >30 who have normal ovulation cycles still have lower pregnancy rates than those women with a BMI between 19-24.
- Some studies show that there is a higher rate of pregnancy loss in women with a BMI >30. The risk of complications during pregnancy such as birth defects, gestational diabetes, and preeclampsia is also higher in these women.
- In men, obesity has been clearly linked to impaired sperm production including low sperm count and low sperm motility and is associated with changes in testosterone levels. Other health conditions such as diabetes, high blood pressure, elevated cholesterol, and being overweight can contribute to erectile dysfunction.
Women with a BMI >40 should seek further treatment as advised by their physician. We also encourage both partners to have a primary doctor and to be aware of family health history especially in regards to diabetes, blood pressure, and cholesterol.
In both men and women, incorporating a healthy diet and regular exercise are first line interventions in weight management. Even a 5-10% decrease in weight (in an overweight individual) can lead to major health changes, including a boost in fertility.
Exercise and Fertility
Research suggests that moderate physical activity in women improves time to pregnancy across the range of BMI. An inverse association between vigorous physical activity and how long it took to become pregnant was found for women with a BMI < 25. In women with a BMI >25 there was no association between vigorous exercise and a longer time to pregnancy. This suggests that in women with a normal BMI, vigorous exercise can be counterproductive, while in overweight women intense exercise does not impair or delay achievement of pregnancy.
A healthy amount of exercise in men is beneficial and even increases sperm concentration. Physically active men who exercised at least three times a week for one hour typically scored higher in almost all sperm parameters in comparison to men who were sedentary or who participated in highly vigorous exercise. Extreme exercise causes oxidative stress which can damage sperm. A research study examining the effect of exercise on men showed that bicycling more than five hours per week has a correlation with both lower sperm counts and lower sperm concentration.[ii]
In addition to maintaining an ideal weight, regular exercise has the following health benefits:
- Reduces physical and mental stress. Improves mood.
- Sharpens your mental acuity and ability to concentrate
- Promotes digestive health
- Strengthens cardio-respiratory system, increases muscle mass, lowers high blood pressure, and decreases high cholesterol and triglycerides
- Promotes good quality sleep
- In addition to a reduction on a variety of other diseases, exercise significantly reduces risk for diabetes (including gestational diabetes during pregnancy) and increases insulin action even in the absence of weight loss. For patients who may be taking insulin sensitizers (such as Metformin), exercise increases the effectiveness of the medication. In fact of all the lifestyle modifications, exercise probably has the greatest ability to improve insulin sensitivity.
All adults should avoid inactivity. Some physical activity is better than none, and adults who participate in any amount of physical activity gain some health benefits. For inactive adults (less that 75 minutes of activity/week), start by building 10 minutes of structured activity into your day.
For substantial health benefits
For more extensive health benefits
For additional health benefits
Aerobic activity should be performed in episodes of at least 10 minutes, and preferably, it should be spread throughout the week. [iii]
Exercise During Treatment Cycle
Now, how does the above information relate to a woman in a fertility treatment cycle? We generally instruct our patients who are cycling to avoid vigorous physical activity. When a patient is taking fertility medications, the ovaries swell and the chance of ovarian torsion (or twisting) is increased especially in the presence of intense physical activity. Moderate activity is generally encouraged throughout the process as it provides many health benefits as previously listed.
Exercise During Pregnancy
The American Congress of Obstetrics and Gynecologists (ACOG) recommends that healthy pregnant women engage in 30 minutes of activity on most days, if not every day. The key is moderation and refraining from activities that are especially jarring and excessively strenuous. In addition to providing mom with health benefits as mentioned before, exercise during pregnancy has some very specific health benefits for both mother and baby:
- Helps prevent or treat Gestational Diabetes
- Helps maintain fitness and improves ability to cope with labor and recover after delivery
- Provides far reaching heart-health benefits to the baby
- Increases heart rate variability (a sign of a strong fetal heart) and strengthens the heart increasing the ability of the baby to cope with the stresses of labor. The benefits to the baby’s heart continue into the child’s first years of life! iv
Exercising during pregnancy is one the very best things you can do for yourself and your child!
iv Early Hum Dev. 2010 Apr;86(4):213-7. doi: 10.1016/j.earlhumdev.2010.03.002. Epub 2010 Mar 30