One in three women who have their first baby through infertility treatment, become pregnant again naturally within two years of their first birth, a new study has found.
A Monash University study, published in the Australian and New Zealand Journal of Obstetrics and Gynaecology, was the first to examine the rates of unexpected conception in Australian women who had a first child through assisted reproductive technology (ART).
The study of 236 women who had a baby through assisted reproductive treatments found 33 per cent of them conceived a second child naturally within two years of their first birth.
Women whose infertility was initially diagnosed as 'unexplained' were more than twice as likely as others with a specific infertility diagnosis to become pregnant naturally.
Lead researcher Dr Karen Wynter, from the Jean Hailes Research Unit at Monash University, said unexpected pregnancies in some of the women could be associated with undiagnosed infertility such as endometriosis.
"It is possible that some of the women had undiagnosed endometriosis and that might be why they were struggling the first time," Dr Wynter said.
''The pregnancy itself actually helps to alleviate some of the symptoms associated with endometriosis and the second pregnancy comes around easier.''
The women who became pregnant naturally were also more likely to have been in relationships for a shorter period of time.
''One possible explanation is that these women are having sex more frequently,'' Dr Wynter said.