Women in their 40s who undergo fertility treatment in order to get pregnant are less likely to be successful if they are aged 43 or older, a new Irish study has found.

According to researchers from Rotunda IVF, in recent decades, the number of women over 40 seeking assisted reproductive technology (ART) to become pregnant has increased worldwide, including here in Ireland.

"This is due to an increase in the average age at which women are choosing to have their first child while additionally, many couples are choosing to have a second family later in life. However, as with natural conception, ART success rates decrease with maternal age," they noted.

They carried out a study of all the women aged between 40 and 45 who had undergone ART at the Rotunda IVF Clinic (previously known as the HARI Clinic) between January 1997 and January 2013.

This clinic has a cut-off limit for ART of 45 years of age. Specifically, the women studied had undergone in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI).

The researchers noted that the number of women in the 40-45 age group increased significantly over the study period. In 1997, they accounted for 7% of the clinic's patients. By 2013, they made up almost 20% of its patients.

The study found that the clinical pregnancy rate was ‘significantly lower' in the 43-45 age group compared to the 40-42 age group - 5% compared to 12.5%. The rate of pregnancy loss was also ‘markedly increased' among those aged 43-45 - 56% compared to 34% in those aged 40-42.

"Women over 40 represent the fastest growing population of patients seeking ART in our clinic, with numbers increasing dramatically from 17 years ago. Our data shows that female patients with an age greater than 42 have a diminished prognosis following IVF/ICSI compared to patients between 40 and 42 years of age," the researchers said.

They noted that this corresponds with previously published data ‘which clearly shows a cut-off for success following ART in women to be 44 years of age'.

"In our clinic, the cut off rate for ART is 45 years of age. This study has enabled better counselling of patients beyond this cut off point as to the ethics associated with this decision," they said.

Details of these findings are published in the Irish Medical Journal.