Why is it you have to be a certain BMI for IVF?

Why is it you have to be a certain BMI for IVF?
too fat. or skinny..not a healthy candidate for IVF
It is for mediacl reasons, if u r obese then often oestrogen in women is depressed and can come back naturally if weight is lost without any need for the IVF. So it is to make sure that the person really needs the treatment, also IVF becomes less safe the more under/over weight you are, so there is that to be considered.
Its hardly that they want to ban larger mums!
BMI body mass index is better to be under 25 for women but above 19 to be healthy. The more healthy u are the better chance u have of conceiving using IVF or the good old fashioned way. If you are healthy there is a better chance of the baby being healthy and also a better chance of carrying the child to full term. Giving birth is no joke when overweight or with poor muscle-tone it would be a lot harder.
BMI is basically to determine how much body fat you have and whether it is feasible to get pregnant and then stay pregnant with a baby. The goal is for you both to be healthy and you staying healthy with neither you or the baby suffering
I have been above and below the recommended BMI and somewhere in the middle is definitely healthier hope this helps