How the most human of errors led to a woman giving birth to a stranger’s baby

A misplaced embryo in a Monash IVF laboratory, which was written off as a counting error for up to a year, ultimately led to a woman giving birth to a stranger’s baby.

The fallout from that error has caused heartbreak for two families, sent shockwaves through thousands of others relying on fertility treatments, tarnished the reputation of one of the world’s oldest and most respected IVF businesses, and forced an urgent overhaul of Australia’s reproductive technology sector.

Credit: Monique Westermann

The fact it needed a perfect storm of circumstances for the error to be discovered – involving a defecting doctor, a Supreme Court battle and the big-money stakes that result in specialists and their patients swapping between rival clinics – has also heightened fears similar embryo mix-ups have gone undetected before.

An investigation by this masthead into the Monash IVF embryo mix-up that led to a Brisbane woman giving birth to another woman’s biological child has uncovered a basic mistake, never thoroughly investigated at the time, that had life-changing ramifications.

This masthead spoke to seven sources involved in the IVF industry, who asked not to be named because of the sensitivity of the issues.

Monash IVF implanted an embryo in the wrong woman.Credit: Luis Enrique Ascui

We have chosen not to identify those involved in the bungle, including the doctor who oversaw the birth mother’s care, to protect the welfare of the child involved.

The error

Rose (not her real name) was given the news that a number of her eggs had been successfully fertilised into embryos, to be frozen for future use.

In a completely separate process, Isabel (not her real name), was being treated at Monash IVF’s busy Brisbane clinic to undergo a transfer in which one of her own fertilised eggs was supposed to be placed into her uterus.

What nobody realised then was that one of Rose’s embryos was not kept frozen with her others and, somehow, it had been transferred into Isabel.

Isabel’s own embryo, which was supposed to be implanted in her uterus, was instead kept frozen with her others that were intended for future use.

The exact circumstances of how Rose’s embryo came to be implanted in Isabel are the subject of an ongoing investigation.

The first sign

Months later, Isabel’s transfer had resulted in a successful pregnancy and her dreams of motherhood were realised, while Rose was still planning to use her own frozen embryos.

However, Monash IVF embryologists were surprised to discover that Rose had one fewer embryo than had been recorded.

The embryologists put the discrepancy down to a counting error during the freezing process, and no formal audit was undertaken at the time.

The error was explained to Rose as a miscount that had left her with one fewer embryo than first thought, without any indication there might be a far greater issue.

Regardless of the failure to pick up on the first sign of a problem, it was too late to change the outcome.

The circumstances

The embryo bungle occurred at a time Monash IVF was rapidly scaling up its Queensland business, almost doubling its Brisbane specialists and placing increased pressure on embryologists working in its Spring Hill laboratory.

As part of its commercial expansion, Monash IVF acquired ART Associates in July 2022 and later relocated its Brisbane clinic to ART’s Spring Hill day hospital, gaining another six specialists in the process.

In early 2023, Monash IVF poached more fertility specialists from its biggest rival clinics, and Monash IVF’s Brisbane team had suddenly grown from 10 to 19 specialists in a matter of months.

As a result, the number of cycles undertaken by Monash IVF in Queensland jumped by more than a third in 2023. Three sources, who asked not to be named due to commercial arrangements, said the increase overwhelmed the Spring Hill laboratory, frustrated long-term doctors and placed huge pressure on embryologists.

By mid-2024, one of Monash IVF’s long-term specialists – who had overseen Isabel’s treatment – “fell out” with the increasingly busy fertility giant over their declining access to the theatres they needed to treat patients.

Frustrated that Monash IVF’s commercial growth was hampering existing specialists’ ability to treat patients, the fertility doctor told the Brisbane clinic that they were leaving.

The doctor told Monash IVF they intended to provide their existing patients with the details of a rival clinic where they could continue to be treated. Those patients included Isabel.

This masthead is not suggesting this doctor was involved in the embryo bungle, only that one of their patients was involved in the mix-up and gave birth to the biological child of another woman as a result.

The court action

Six weeks later, Monash IVF began legal action in an attempt to prevent its former fertility doctor taking patients to the rival clinic.

Monash IVF asked the Supreme Court of NSW to issue an injunction banning the doctor from having a commercial interest in or working at a clinic within 50 kilometres of its Spring Hill clinic for at least six months. The ban would have prevented many existing patients from continuing to see the doctor, and instead have them remain with Monash IVF under the care of another of its growing team of specialists.

However, the court ruled against Monash IVF and found patient welfare was more important than its commercial interests.

“Restraining [the doctor] from practising would have caused prejudice to [their] patients,” the Supreme Court found.

“Counsel for Monash argued that Monash would be able to replace [the doctor] with alternative doctors to avoid this prejudice. The doctor-patient relationship is a confidential and personal one and for this reason I did not consider that counsel’s proposal was satisfactory.”

The judge also raised questions about the timing and lack of notice of Monash IVF’s legal action.

”There was no explanation, or evidence, as to why the matter was only brought before the court, urgently, six weeks (at least) later. I considered this to be a factor which prejudiced [the doctor],” the judge found.

On December 19, 2024, the court ordered Monash IVF to pay the doctor’s costs for its unsuccessful Supreme Court action. The court’s earlier ruling had also made it viable for the doctor’s patients – including Isabel – to follow the doctor to their new clinic.

The shocking discovery

If the doctor had remained working at Monash IVF, or if the Supreme Court had blocked them from taking their patients to the new clinic, the embryo mix-up might never have been discovered. Instead, the defection and court ruling meant Monash IVF embryologists were tasked with auditing and preparing embryos and other frozen donor material to be sent to the doctor’s new employer.

While preparing Isabel’s remaining frozen embryos for relocation on February 10 this year, embryologists discovered they had one more embryo than they should have.

Two days later, on February 12, an initial Monash IVF investigation connected the dots between Isabel’s newly discovered frozen embryo and the one missing from Rose that had been dismissed as a miscount some time earlier.

The answer was unthinkable, but confirmed: Monash IVF had mixed up the women’s embryos, and Isabel had unknowingly given birth to Rose’s biological child.

The fallout

Monash IVF immediately contacted Rose and Isabel to apologise, offer counselling and begin mediation to try to find an outcome for a situation that has no legal or moral precedent in Australia.

On March 4, the company also commissioned Fiona McLeod, SC, to conduct an independent investigation into the mix-up. But within two months, news that IVF’s worst nightmare had happened in Brisbane was filtering through Australia’s fertility industry. It eventually made national headlines on April 10.

As Monash IVF’s reputation and share price plummeted, the Australian Stock Exchange demanded to know why the fertility giant had not informed shareholders sooner. While the company’s response admitted it had been aware of the bungle since February 10, it made no mention of the missing embryo it had first noticed, then dismissed, up to a year earlier.

“[Monash IVF] became aware of the incident on 10 February 2025. It became aware of the results of the initial investigation, namely that the incident was the result of human error, on 12 February 2025,” the company told the ASX.

Just two months later, Monash IVF admitted a second bungle had resulted in a Melbourne woman being implanted with the wrong embryo at its Clayton clinic on June 5. In that incident, the woman’s own embryo, rather than her partner’s, had been mistakenly transferred.

Public shock over the two embryo mix-ups followed a $56 million settlement Monash IVF had agreed to in August 2024 after a class action involving more than 700 families who might have had their viable embryos needlessly destroyed due to a faulty genetic testing program.

Monash IVF chief executive Michael Knaap resigned on June 12, and McLeod’s investigation has now been expanded to determine if wider systemic issues are occurring within the embattled fertility giant.

The fallout is also extending to the entire fertility industry, with the country’s health ministers having ordered an urgent review on June 13 to find a more stringent way of regulating the lucrative assisted reproductive technology sector and ensure patients are put before profits.

But on June 16, within three days of the ministers’ announcement, Monash IVF turned to Victoria’s Supreme Court to again try to block one of its senior staff – former chief operating officer Hamish Hamilton, who had overseen the Brisbane recruiting drive and sudden scaling up of its business – defecting to a rival clinic.

On this occasion Monash IVF was more successful and the court slapped restrictions on Hamilton’s work in his new role at Virtus Health.

A spokesperson for Monash IVF said it would provide an update on the findings of McLeod’s review “in due course”.

“Monash IVF has apologised to the affected patients – we are truly sorry – and we continue to support them. The privacy of the families involved – including the child – has been our priority and is why we have disclosed information about these matters in a de-identified way,” the spokesperson said.

“Monash IVF has implemented additional verification processes and enhanced patient confirmation safeguards over and above normal practice, as well as the continued use of electronic witness systems, to ensure patients and clinicians have every confidence in our processes.”

The Brisbane bungle may help bring long-term, independent oversight to an industry criticised for putting profits before patients. But it will also leave at least two families with a lasting reminder of a health sector that was left to regulate itself.

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