A researcher at an IVF department is working on embryo selection.
Credit: AFP
PARIS: Retrieving about 15 eggs from a woman's ovaries in a single cycle gives the best chance of having a baby through in-vitro fertilisation (IVF), researchers have reported.
Investigators looked at data from the UK's Human Fertilisation and Embryology Authority (HFEA) on 400,135 IVF cycles in Britain between 1991 and 2008 to discover that harvesting around 15 eggs in one go gave the best statistical chance of a live birth. The odds levelled off between 15 and 20 eggs, and then steadily declined beyond 20 eggs.
"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 lead author Arri Coomarasamy from the University of Birmingham in central England of the study published in Human Reproduction.
"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."
Achieving the optimum number of eggs
Using a model, the researchers created a mathematical graph, called a nomogram, which shows the relationship between women's age, the numbers of eggs retrieved and the predicted live birth rate.
Now patients and clinicians can use the nomogram when making decisions about the degree of ovarian stimulation required to achieve the optimum number of eggs for a live birth.
The success rate for 15 eggs in 2006-2007 was 40% among women aged 18-34, 36% for those aged 35-37, 27% for those aged 38-39 and 16 percent for women aged 40 or more.
Avoid wasting precious eggs
The findings should be a useful tool for fertility doctors who want to make IVF as efficient as possible, avoid wasting precious eggs and limit the risk of dangerously overstimulating the ovaries, according to the authors.
"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," said Coomarasamy.
He believes that doctors could combine the use of the nomogram with current methods of measuring a woman's ovarian reserve in order to work out how much her ovaries need to be stimulated in order to retrieve 15 eggs in a safe manner.
Fresh or thawed
IVF treatments entail taking eggs and fertilising them in a lab dish with sperm. Several early-stage embryos are then implanted in the uterus in the hope that one will result in a live birth, although multiple births sometimes result.
Embryos that are not immediately implanted are usually frozen, so that they can be thawed for future IVF attempts.
The data used in the study did not distinguish between live births that resulted from fresh or thawed embryos.
