Want to know your chance of having a baby through in-vitro fertilization? There's an app for that.

British researchers have devised a formula which they say gives a highly accurate prediction of the potential success of IVF, to help couples decide whether to try the treatment.

They have made it available online as a simple computer calculator application, and say it will soon be available for download on Apple's iPhones and other mobiles.

Scientists from the Universities of Glasgow and Bristol analyzed the details of more than 144,000 IVF cycles to produce a statistical model that can give a prediction of live birth which is up to 99 percent accurate.

Treatment-specific factors can be used to provide infertile couples with a very accurate assessment of their chance of a successful outcome following IVF, said Scott Nelson of the University of Glasgow, who led the research.

Nelson, whose work was published in the Public Library of Science (PLoS) Medicine journal, said that up until now estimates of success have not been very reliable.

The formula takes into account the woman's age, number of years trying to get pregnant, whether she is using her own eggs, the cause of infertility, the number of previous IVF cycles and whether she has previously been pregnant or had a baby.

The result of this study is a tool which can be used to make incredibly accurate predictions, he said in a statement.

Nelson's team used data held by the Human Fertilisation and Embryology Authority, which regulates IVF treatment in Britain. They looked at all cycles carried out between 2003 and 2007 and assessed the chances of having a live birth.

The fertility treatment market is big and growing, with an estimated 140,000 IVF cycles in the United States in 2008. As many as 80 million couples worldwide are infertile, experts say.

In the United States and Britain, IVF is successful in about a third of women under 35 years old but in only five to 10 percent of women over the age of 40, Nelson said.

There are many other factors besides age which can alter the chance of success and clinics don't usually take these into account when counseling couples or women, he added.

The calculator is already available free at www.ivfpredict.com. Applications for iPhones and Android smart phones are coming soon, so users can discuss the results with your clinicians right there in the clinic, the website says.

There is a real need in medicine to try and replace general statements such as 'high risk' and 'good chance' with well validated, quantitative estimates of probability, said Gordon Smith, head of Cambridge University's obstetrics and gynecology department, who did not work on the study.

This model...provides women considering IVF with an understandable and quantitative estimate of their chances of success. It is a great resource.

(Editing by Peter Graff)