Is '15' the perfect number for IVF success?

A study of over 400,000 IVF treatment cycles in the UK has found a 'strong association' between the number of eggs retrieved prior to a woman undergoing IVF and live birth rate. The findings suggest that chances of a live birth increased with the number of eggs collected up to the number of 15, after which it began to decline.

'This is the first study to look at the association between the number of eggs and live births. Some smaller studies have reported previously on the association between egg numbers and pregnancy rates, but not live births', said Dr Arri Coomarasamy, one of the authors of the study.

The study analysed data obtained by the UK's Human Fertilisation and Embryology Authority (HFEA) on IVF cycles that took place in the UK between April 1991 and June 2008. It found the more eggs retrieved the greater the live birth rate, up to between 15-20 eggs, where there was no change. After 20 eggs the live birth rate declined.

Normally, women produce only one egg at a time. To increase the chance of implanting a viable embryo, women undergoing IVF take hormones to stimulate their ovaries to produce more eggs. Dr Coomarasamy said: 'Mild stimulation protocols aim to retrieve less than six to eight eggs; a standard stimulation should aim for 10-15 eggs, and we believe this is what is associated with the best IVF outcomes; when the egg number exceeds 20, the risk of ovarian hyperstimulation syndrome (OHSS) becomes high'.

The researchers also created a graph describing the relationship between women's age, the number of eggs retrieved and the predicted live birth rate. This, combined with already existing techniques such as anti-mullerian hormone (AMH) testing and antral follicle count (AFC) which are used for predicting how many eggs will be retrieved after ovarian stimulation, could be useful for helping doctors to predict a woman’s IVF success rate.

The study was published in the journal Human Reproduction.