The cumulative chances of a woman getting pregnant following IVF increase with each treatment cycle until the sixth cycle, after which the increases are minimal, show study results from Australia and New Zealand.
A total of 21, 31, 36, 39 and 40 percent of women of all age groups treated with one, two, three, four, and five IVF cycles respectively in 2009 to 2011 had a live birth. However, women who went on to have more than five cycles did not see a significant increase in their pregnancy chances, at only 0.7 and 0.4 percent for the sixth and seventh cycles.
Lead author of the study, Professor Elizabeth Sullivan, from the University of New South Wales in Sydney, believes it reminds women that 'the earlier you start planning about having a family or accessing fertility treatment if you need to, the better'.
'The other good news is that we expect to see the cumulative success rates increase as women who may have only had one or perhaps two cycles in our study timeframe, return for further treatment - and get pregnant', Professor Sullivan adds.
Other findings from the study show that just over half of women under the age of 35 years will have a baby within five rounds of IVF, compared with just 15 percent of women aged 40 years or older.
In addition, the rate of multiple births decreased during the study period, which Fertility Society of Australia president, Dr Mark Bowman, puts down to 'better single embryo transfer technology' in Australia compared with other countries.
'Twins have higher rates of prematurity which leads to all sorts of problems: premature death, abnormalities, longer-term disability', he said. 'Now those won't happen to all twins but they are much, much higher in twins than they are single babies'.
Dr Bowman added that transferring more embryos into the woman's uterus did not necessarily improve her chances of getting pregnant, and he would never advocate the case to transfer more than two.