IVF and IUI offer similar success rates for couples with unexplained infertility

Researchers at Waipapa Taumata Rau, University of Auckland, conducted a seven-year national trial in New Zealand to compare fertility treatments for couples with unexplained infertility.

The study followed 737 couples who could not conceive despite medical tests showing no clear cause. Participants were split into two groups: one began with intrauterine insemination (IUI), which places sperm directly into the uterus, and moved to in vitro fertilization (IVF) if they did not conceive.

The other group began directly with IVF, which involves fertilizing eggs in a laboratory before transferring an embryo. The trial revealed that nearly 75 percent of these couples had a baby within two years of starting treatment. While IVF produced faster pregnancies, the long-term results were nearly identical for both groups after the two-year period.

Specifically, about half of the participants in the IVF group had a live birth after a single cycle, while one in three couples in the IUI group succeeded after four cycles. The researchers found that IVF achieved a 55 percent success rate, which exceeded their initial predictions. The study findings may influence how New Zealand manages publicly funded fertility care.

The average age of women in the study was 34, and researchers noted that success rates drop as women enter their mid-to-late 30s. Because many couples wait up to seven years before receiving public funding and facing further waiting lists, the researchers argue for increased investment in fertility services. The results also suggest that couples can choose the less invasive IUI pathway first without lowering their chances of eventually having a child.