A landmark University of Auckland study has found nearly three out of four couples with unexplained infertility had a baby within two years of starting treatment, whether they received in vitro fertilisation (IVF) or intrauterine insemination (IUI).
While IVF led to faster pregnancies, researchers found long-term outcomes were similar for both treatments.
The seven-year national trial was led by researchers at Waipapa Taumata Rau, University of Auckland, and supported by six fertility clinics across New Zealand.
One of the largest studies of its kind, it followed 737 couples struggling to conceive despite tests showing no obvious cause.
Couples were randomly assigned to one of two treatment pathways. One group began with intrauterine insemination (IUI) and progressed to in vitro fertilisation (IVF) if they did not become pregnant, while the other group proceeded directly to IVF.
IUI involves placing prepared sperm directly into the uterus at the time of ovulation. IVF involves collecting eggs, fertilising them in a laboratory and transferring an embryo into the uterus.
The study found IVF offered the best chance of having a baby sooner, but both approaches produced virtually the same outcome after two years.
A single cycle of IVF resulted in a live birth for about half of the participants, compared with about one-third of those who underwent four cycles of IUI.
“We found that IVF resulted in more live births, so approximately one in two couples would end up with a baby after doing one cycle of IVF, compared to one in three with IUI,” says Dr Lucy Prentice, a senior lecturer at the University and lead author of the study.
“But if we look at the results at the end of the study, the number of babies was the same in both groups.
“About three out of every four couples ended up with a baby at the end of the two-year trial, which was a fantastic result.”
Unexplained infertility affects about one-third of infertile couples and remains one of the most common reasons for seeking fertility treatment, she says.
The trial compared New Zealand’s two publicly funded fertility options to help determine the most effective approach for these patients.
The research also produced an unexpected result. While IUI performed as anticipated, IVF achieved higher success rates than researchers had predicted before the study began.
“IVF was the surprise, with the great news that we can get 55 percent of couples a baby from this treatment,” says Dr Prentice.
The average age of women in the study was 34. Treatment success declines with age, particularly from the mid to late 30s, she says.
Couples with unexplained infertility typically spend five years trying to conceive before becoming eligible for publicly funded care. Once eligible, many face another 12 to 24 months on an IVF waiting list, meaning a delay of up to six years before starting treatment.
“Having access to publicly funded fertility care has made a huge and positive difference to the lives of many previously childless couples,” says Dr Prentice.
Professor Cindy Farquhar, principal investigator of the FIIX trial and a professor in the Department of Obstetrics and Gynaecology at the University of Auckland, says the findings should help guide future decisions about access to publicly funded care.
“Funding for fertility treatment has not increased since 2005, despite increasing numbers of people needing care,” she said.
“The results suggest we should be investing more in fertility services so people can access treatment earlier. I hope these findings contribute to a national discussion about how we can better support people experiencing infertility.”
The team plans to share the evidence with health services and funders while continuing work on the cost-effectiveness of different fertility pathways.
Dr Prentice says the results provide reassurance for couples facing unexplained infertility.
“Treatment is effective for this condition. They should not lose hope because even after very long periods of trying to conceive unsuccessfully, we’ve proven that in this poor prognosis group, we get a really fabulous result for these couples.”
The findings also suggest couples can choose a less invasive pathway without compromising their chances of success, she says.
“If couples want to take a slower, less invasive approach and start with IUI before progressing to IVF, that doesn’t negatively impact their chance of having a baby within two years. That means the choice can be guided by the couple’s preferences.”
