My Weight – My Fertility



If you are thinking about getting pregnant or trying, it is important to be aware of how exercise, or lack of exercise may be affecting your natural fertility. The fact is most of us never think that exercise can impact our infertility however too much or too little exercise may delay or even prevent you from becoming pregnant.

It’s widely accepted that obesity has a negative affect on our fertility, but did you also know that over exercise and low body weight (BMI) may also affect fertility.

What is BMI? Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women, regardless of gender, age, or frame size.

What’s so important about BMI? Being too thin (a body mass index of less than 18.5) or overweight (a BMI of 25 or more) may affect your natural fertility and additional research shows obesity may increase the risks of complications during pregnancy and even your baby’s health. If you are concerned about your weight you should consult your General Practitioner.

Use our tool to calculate your pre-pregnancy BMI. This will give you a starting point for recommended weight gain or loss.

Calculate your BMI here
less than 18.5  = I am underweight
Between 18.5–24.9 = I am normal weight
Between 25–29.9 = I am Overweight
BMI of 30 or greater = I am classified as being Obesity

Some research about being Overweight
Danish researchers in a study of over 5000 men found a link between obesity in men and lower sperm count compared to normal weight men(1)  and in the same study found a lower IVF success rate for women with a BMI over 35 (13% compared to 19% among healthy weight women). They were also less likely to become pregnant after two in-vitro fertilization attempts (22% became pregnant v/s more than 20% of normal or underweight women. If you are overweight, losing 5 percent to 10 percent of your current weight is often enough to improve ovulation.

About being Underweight

A Harvard researcher, Professor Rose Frish (2) has conducted a range of studies showing how under nutrition and intense physical activity can have a limiting effect on female fertility. Women who have too little body fat, because of over dieting and/or intensive physical activity show a disruption or impairment of their reproductive ability . If you are too lean, gaining 2-5kg can sometimes be enough to restart ovulation and menstrual periods.

1.  Jensen, T. Fertility and Sterility, October 2004; vol 82: pp 863-870. Ryley, S. “Influence of body mass index (BMI) on the outcome of 6,827 IVF cycles,” presented at the annual meeting of the American Society for Reproductive Medicine, Philadelphia, Oct. 16-20, 2004.

2.  Rose E. Frisch Associate Professor of Population Sciences, Emerita Member, Harvard Center for Population and Development Studies Department of Population and International Health


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