MELBOURNE, Australia: A second embryo mix-up in just two months has pushed one of Australia's largest IVF providers back into the spotlight, prompting calls for stronger national oversight and raising fresh concerns among patients.

Monash IVF said a woman undergoing treatment at its Melbourne clinic was mistakenly implanted with her embryo instead of one created with her partner's sperm, as intended. The incident occurred on June 5 and is now being investigated by regulators.

The company said it was supporting the unidentified couple but did not elaborate on how the mistake was discovered or what the couple planned to do next. "The patient's embryo was mistakenly implanted under a treatment plan which called for an embryo from the patient's partner to be transferred," Monash IVF said in a statement.

The incident adds to the fallout from a separate case disclosed in April, in which a Brisbane woman gave birth to a stranger's child after an embryo mix-up in 2023. That case was widely reported as the first of its kind in Australia and shook public confidence in the sector.

"This mix-up, the second reported incident at Monash IVF, risks shaking confidence not just in one provider but across the entire fertility sector," said Hilary Bowman-Smart, a researcher and bioethicist at the University of South Australia.

Founded nearly 50 years ago, Monash IVF was behind the world's first IVF pregnancy and, according to industry figures, today, carries out nearly 25 percent of Australia's 100,000 assisted reproductive cycles annually.

The company's shares plunged 25 percent by midday on June 10, dragging them to just over half their value before the Brisbane incident. "We had thought the Brisbane clinic embryo transfer error was an isolated incident," said RBC Capital Markets analyst Craig Wong-Pan. "We believe there is now risk of a greater impact of reputational damage and market share losses to MVF's operations."

Monash IVF had already commissioned an independent investigation after the Brisbane case and said it would expand the inquiry's scope to include the new error. It has also begun installing additional interim safeguards around embryo verification.

The company reported the Melbourne incident to the Victorian Department of Health and the Reproductive Technology Accreditation Committee (RTAC), part of the Fertility Society of Australia.

Victorian Health Minister Mary-Anne Thomas said the department was investigating both the company and the incident. "Families should have confidence that the treatment they are receiving is done to the highest standard," she said. "It is clear Monash IVF has failed to deliver that, which is completely unacceptable."

Fertility Society president Petra Wale acknowledged the emotional toll on the couple involved but stressed that such mistakes remain rare. Society has repeated its call for nationally consistent laws around IVF.

Australia's IVF sector is currently overseen by a mix of state health departments and self-regulating industry bodies, a framework some experts say is overly complex.