A couple wanting to know their chances of having a baby through in-vitro fertilization (IVF) can now take heart with an application to give them an answer.

British researchers have devised a formula that will help them give quite an accurate prediction of the success of IVF treatment or otherwise what is known as a test tube baby, Reuters reported.

Eager ‘infertile’ couples can now decide whether to try the treatment as researchers have made this formula available as a simple computer calculator application, which will soon be available for download on Apple’s iPhones and other mobiles.

A statistical model has been produced by scientists from Universities of Glasgow and Bristol that can predict 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,” the report quoted Scott Nelson of the University of Glasgow as saying, who led the research.

He said the formula involves taking the woman’s age into consideration, the number of years she has tried to get pregnant and whether she is using her own eggs. It also takes into account the cause of infertility, the number of previous IVF cycles and whether she had been previously pregnant or had a baby.

“The result of this study is a tool which can be used to make incredibly accurate predictions,” said Nelson, whose work was published in the Public Library of Science (PLoS) Medical journal.

The team studied the data held by Human Fertilisation and Embryology Authority that regulates IVF treatment in Britain and all the IVF cycles carried out between 2003 and 2007 to assess the chances of having a live birth.

Experts say there are as many as 80 million infertile couples worldwide with the fertility market growing at an estimated 140,000 IVF cycles in the US in 2008.

Nelson said IVF is successful in about 33 percent of women below 35 years of age but in only 5 percent to 10 percent of women over 40 years of age in the United States and Britain.

There are many other factors besides age that can alter the chance of success, he said. “Clinics don't usually take these into account when counseling couples or women”, Nelson said.

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

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, the report quoted Gordon Smith, head of Cambridge University's obstetrics and gynecology department, as saying, 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,” he said.