By Dr Anita Star
Setting a New Year’s resolutions about getting your body fit, doing lots of exercise and becoming healthy in order to maximise your fertility? Wooooooooo- up girlfriend. Let’s arm you with some information first.
There is such a thing as too much exercise, and of course there is also a problem of too little. The tricky thing is, different bodies respond differently to exercise, and the relationship between exercise and fertility is very complex. I am going to talk you through some different research studies and then I would strongly recommend you talk through advice specific to your individual circumstances with your doctor or fertility specialist.
Ok so in the first study was from women in the general community. It involved a 10 year follow up study of around 3800 women from the general population in Norway (Gudmundsdottir et al). After controlling for other factors affecting fertility (age, number of pregnancies, education, alcohol consumption, marital status, education, and it also considered BMI in a separate analysis) their findings included.
- women who were active on most days of the week were 3.2 times more likely to be infertile than inactive women. Exercising to exhaustion was associated with 2.3 times the odds of infertility compared with lower levels of intensity.
- For duration, there was decreased risk of infertility in those whose exercise was moderate (16–30 and 30–60 minute sessions), compared with the shortest duration of less than 15 min.
- However women who, who were highly active (>60minute sessions, or exercising to exhaustion) had more infertility compared women with low or moderate levels of activity.
- They looked at young women up to age 30 separately and found subfertility was reported by 23.7% of those exercising to the level of exhaustion and by 11.1% of those who reported exercising almost every day.
- In the young women subgroup the rate of subfertility for those exercising for less than 15 minutes was 12.6% and those exercising more than 60 minutes was 12.4%; whilst those exercising between 16 and 30 minutes the rate of subfertility was much lower at 3.9%, and around 7% for those exercising between 30 and 60 minutes.
So to summarise this Norwegian study, complete inactivity i.e. less than 15 minutes exercise at a time was associated with infertility and subfertility, regardless of BMI (a marker of obesity). But also excessive exercise i.e. greater than 60 minutes exercise at a time, or exercising to exhaustion or exercising every day was associated with infertility and subfertility.
Another study conducted in the general community was of 3600 women in Denmark (Wise et al). They similarly found the effects of physical activity on fertility differed according to the intensity of physical activity, but also in this study there was a different relationship depending on if you were overweight or not. The definitions of vigorous activity in this study included running, fast cycling, aerobics, gymnastics, or swimming; whilst moderate activity was defined as brisk walking, leisurely cycling, golfing, or gardening. They found vigorous physical activity was associated with delayed time to pregnancy; unless you were overweight in which case it did not delay time to pregnancy. Moderate physical activity was associated with decreased time to pregnancy regardless of weight status. The authors conclude that ‘physical activity of any type might improve fertility among overweight and obese women, a subgroup at higher risk of infertility. Lean women who substitute vigorous physical activity with moderate physical activity may also improve their fertility’.
The next couple of studies focused on women undergoing assisted reproductive technology.
Ferreira et al looked at 436 women undergoing intracytoplasmic sperm injection cycles. The main finding in relation to physical activity showed 1 hr of activity 3 times per week was associated with positive outcomes including- increased implantation, increased pregnancies and decreased miscarriages. It was also associated with decreased BMI.
The next study (morris) was of around 2000 patients undergoing IVF in the USA. In this study they looked at the relationship between exercise and outcomes including cycle cancelation, failed fertilisation, implantation failure, pregnancy loss and successful live birth. The study did also take into account other variables which may impact upon pregnancy outcomes including, BMI, use of alcohol, caffeine, and tobacco. There were some complex findings specifically
- women who reported regular exercise were no more likely to have a live birth compared with those women who did not report exercise
- Women who reported exercising 4 hours or more per week for 1–9 years were 40% less likely to have a live birth and were almost three times more likely to experience cycle cancellation or pregnancy loss than women who did not report exercise.
- However negative outcomes were not found in women who exercised less intensely i.e. 1-3 hours per week; or among women who had exercised for 4 or more hours per week for more than 10 years (I take that to mean they had pretty much always exercised to this level over their entire lives).
- In general, women who participated in cardiovascular exercise such as running had poorer outcomes (30% less chance of successful live birth) compared to women who reported no exercise, or women who did less intense activity such as walking.
So it is quite a complex picture. There are benefits to regular low to moderate activity on your fertility outcomes, particularly if you are overweight. However, there are also negative consequences of doing too much exercise. And, if you are an exerciser, the bar for what is considered too much exercise in these studies is actually set pretty low; that is relative to what I know many active women do each week. So have a think through all of this and have a chat with your doctor, you may need to do some more exercise, or you may need to do less, depending on your circumstances. If you have been struggling for a while with fertility issues, you could alter your current approach to exercise, to see if that makes a difference.
Take care everyone. For all who are #TTC, wishing you lots of baby dust, prayers and all the goodness of Mother Nature in 2018.
Ferreira, Renata Cristina, et al. “Physical activity, obesity and eating habits can influence assisted reproduction outcomes.” Women’s Health 6.4 (2010): 517-524.
Gudmundsdottir, S. L., W. D. Flanders, and L. B. Augestad. “Physical activity and fertility in women: the North-Trøndelag Health Study.” Human Reproduction 24.12 (2009): 3196-3204.
Morris, Stephanie N., et al. “Effects of lifetime exercise on the outcome of in vitro fertilization.” Obstetrics & Gynecology108.4 (2006): 938-945.
Wise, Lauren A., et al. “A prospective cohort study of physical activity and time to pregnancy.” Fertility and sterility 97.5 (2012): 1136-1142.