Fertility doctors should retrieve about 15 eggs from a female’s ovaries in one cycle if they want her to have the best chance of giving birth to a child after assisted reproduction technoloqy, researchers at the University of Birminham, England wrote in the journal Human Reproduction. The authors found there is a strong link between live birth rates and the number of eggs that need to be recovered in one cycle.

The live birth rate peaked when approximately 15 eggs were retrieved, and remained about the same at between 15 and 20 eggs, and then dropped.

Co-author, Dr Arri Coomarasamy, said:

“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. This is also the first study to devise a graph that can be used by patients and clinicians to estimate the chances of a live birth for a given number of eggs.”

Dr Coomarasamy, and team evaluated data from HEFA (Human Fertilisation and Embryology Authority, UK), which contains 400,135 IVF cycles that occurred throughout the United Kingdom between April 1991 and June 2008. As the live birth rate progressively improved, the investigators gathered data form 2006-2007 to create a predictive model that reflected current practice as closely as possible.

They then created a momogram, a type of mathematical graph, which shows the relationship between the predicted live birth rate and a woman’s age, as well as the total number of eggs retrieved. Patients and doctors can now utilize the nomogram when deciding on the level of ovarian stimulation needed to get the best number of eggs for a live birth.

Dr Coomarasamy said:

“Our data show that around 15 eggs may be the best number to aim for in an IVF cycle in order to maximise the chances of a live birth while minimising the risk of ovarian hyperstimulation syndrome (OHSS) which is associated with a high number of eggs, usually over 20. 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 OHSS becomes high.”

Clinicians may combine the use of the nomogram with current methods of calculating a female’s ovarian reserve in order to decide on the level of stimulation of the ovaries required so that 15 eggs can be retrieved safely.

He said:

“There are tests of ovarian reserve such as anti-mullerian hormone (AMH) and antral follicle count (AFC) which are good at predicting ovarian response and the egg yield following ovarian stimulation during IVF treatment. However, AMH and AFC are not good predictors of live birth rates. If clinicians use AMH or AFC to estimate the egg yield, they can then use our nomogram to convert this estimated number of eggs into a predicted live birth rate, thus completing the prognostic chain to estimate the chances of what both they and the women want: a live born baby.”

The predicted live birth rate for females with 15 eggs retrieved during 2006-2007 was:

  • Ages 18 to 34 – 40%
  • Ages 35 to 37 – 36%
  • Ages 38 to 39 – 27%
  • Ages 40+ – 16%

Researchers cannot currently use the HFRA data to link information on IVF cycles using fresh embryos with frozen embryos in the same patient. Knowing this could change the reducing effect on fresh IVF cycles, because a woman has a better probability of becoming pregnant if frozen embryos are ready for transfer in the following cycles.

The authors write, however, that:

“Existing data suggest that the numbers of embryos frozen after a fresh IVF cycle are not enhanced by retrieving more than 18 eggs.”

Dr Coomarasamy added:

“The HFEA have agreed to provide data linking fresh and frozen cycles to answer this research question and they may be releasing this information soon. By including the outcome following replacement of all frozen embryos generated from a single fresh IVF treatment, we could give an estimate of the cumulative live birth rate per IVF cycle. This is important information and we hope to gather the necessary data and report on this outcome in the future.

None of this work would be possible without the support of the HFEA and we are very grateful to the staff there who validated these data.”

“Association between the number of eggs and live birth in IVF treatment: an analysis of 400 135 treatment cycles”
Sesh Kamal Sunkara, Vivian Rittenberg, Nick Raine-Fenning, Siladitya Bhattacharya, Javier Zamora and Arri Coomarasamy
Hum. Reprod. (2011) doi: 10.1093/humrep/der106

Written by Christian Nordqvist