Sonia Kruger her daughter Maggie, who was conceived using a donor egg from a younger woman. Kruger gave birth at age 49.

It’s an industry built on wishful thinking and has been criticised by some for giving women false hope.

Doctors say the best way to help women through this emotional and expensive process is to be honest with them about the statistics. Once they know how likely they are to fall pregnant, they can make an informed choice about whether to proceed with treatment.

A new large-scale study released today does exactly that, and found two thirds of women under 40 starting fertility treatment will have a baby within five years.

There is continuing debate on how to best measure the “success” of fertility treatment, but the authors of the Danish study claim they’ve been able to provide couples with a “reliable” long-term predictor of success — based on years, not on IVF treatment cycles.

The comprehensive study, led by Dr Sara Malchau of Copenhagen University Hospital, analysed the birth records of more than 20,000 women who had fertility treatments in Denmark between 2007 and 2010.

Results showed that after two years 57 per cent of women had a baby through the use of either IVF or intra-uterine insemination (IUI).

Total births increased to 65 per cent after three years, and to 71 per cent after five years. Further analysis showed age was the greatest determinant of success.

At five years, total birth rates were 80 per cent for women under 35 years, 60.5 per cent for those aged 35-40, and 26 per cent for those aged 40 and over.

Singer Janet Jackson, 50, is expecting her first child with Wissam Al Mana. Experts say it is virtually impossible for women over 45 to conceive without a donor egg from a younger woman. Picture: Vittorio Zunino Celotto/Getty ImagesSource:Getty Images

Overall chances of a live birth are good, but the point that the study makes is that successful treatment takes time, says Dr Gareth Weston, acting medical director at Monash IVF Group.

He says it’s important for any couple to be properly assessed to determine whether they actually need IVF in the first place. Many problems will be able to be corrected before the use of reproductive assistance, such as removing endometriosis in women or a cyst blocking a fallopian tube.

He urges couples not to rush into IVF and to exhaust all other options first, such as IUI.

One way or another, women under 40 willing to persist with treatment will achieve a baby in the vast majority of cases, Dr Weston said. “I always say to my patients it’s a marathon and not a sprint.”

But Associate Professor Mark Bowman from the Fertility Society of Australia says he disagrees with doctors who say couples should try IVF over and over again until they fall pregnant.

“Whether you’re 40 or 30, the majority of people who are destined to conceive will do so in the early part of their treatment,” Assoc Prof Bowman told news.com.au.

“The pregnancy rate on your first cycle of IVF is much higher than the pregnancy rate if you’re on the fourth cycle, even if you’re the same age. Ninety per cent of the people who are going to be successful get that within the first three attempts of IVF,” he said.

Dr Weston says it’s essential women over 40 are given accurate information, because the statistics are very different for this age group. For women over 40, the chances of a live birth from IVF is 18 per cent.

These rates drop significantly by a woman’s 41st birthday, according to data obtained by the ABC’s Four Corners program, which in May aired a special investigation into Australia’s IVF industry.

If you’re aged 41-42, there’s a 5.8 per chance of a live birth through IVF. For those aged 43-44, that drops to 2.7 per cent. If you are over 45, it drops even further to 1.1 per cent, or a 99 per cent chance of failure.

“As they approach 45 from 40 the success rates do drop off significantly and that is the group which needs to have very careful and accurate information about the chances of success,” said Dr Weston.

If an IVF clinic is not willing to reveal their success rates before the start of treatment then that service should not be used, advises Dr Weston.

rebecca.sullivan@news.com.au