Why does an egg donor’s BMI matter?

BMI

To qualify to become an egg donor in South Africa, you must meet a strict set of guidelines. You must be a certain age (between 19 and 32), be drug-free, have good family medical history, your BMI must be between 18 and 28 points.

The BMI requirement is one that we’re asked about a lot – so we’re taking some time to break it down.

What is BMI?

BMI stands for Body Mass Index, it’s a mathematical way of measuring how ‘healthy’ your size is, based on your weight and height. If you’re into the maths, the formula is this: Your weight (in kilograms) divided by your height (in centimetres) squared, then multiplied by 10 000. If you’re not into the maths, there are literally thousands of BMI calculators online.

While it doesn’t directly measure your amount of body fat, BMI is still the measurement that many medical professionals use to establish whether a person is ‘normal’, overweight, or underweight.

A ‘normal’ BMI is between 18.5 and 24.9 points, while ‘overweight’ is classified at between 25 and 29.9 points, and ‘obese’ at 30 points and above.

So, what does it matter?

Your BMI not only impacts the quality of your own eggs, but also how you might respond to the fertility drugs that you’re given.

Research has proven that women with an ‘abnormal’ (high or low) BMI are less likely to fall pregnant in the same period as women with a ‘normal’ BMI. There is a ton of science behind it, but a lot of it has to do directly with those fatty bits (also known as adipose tissue), which release hormones and proteins that can get in the way of healthy egg development and ovulation. For example – adipose tissue releases some oestrogen (who knew?) A healthy balance of oestrogen is critical for healthy ovulation – more adipose tissue means more oestrogen, throwing your body’s delicate hormonal balance out of whack.

But most importantly, women who are overweight also typically have a lower response to the medication prescribed, requiring a larger / longer dose of the egg stimulating medication that you’re given. These higher doses, somewhat counterintuitively, could lead to fewer healthy eggs being retrieved – which could lead to a lower success rate for your recipients.

Other risks

Aside from the meds not working as they should, a very high or low BMI can impact how your body responds to the anaesthetic that is administered during your retrieval and make it difficult for the doctors to physically perform the retrieval. It puts our donors at risk and that’s the last thing we want!

So, if you’re looking to donate your eggs and your BMI falls out of the required range, it’s a perfect motivation to make any lifestyle changes that you might need. Just make sure not to do anything drastic without the help of a medical professional!