Why a 20-year-old study claiming a baby died from opioid poisoning through breast milk is still under fire

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A controversial Canadian medical paper, which pinned a baby’s death on codeine passed through breastmilk, is under renewed scrutiny a full two decades after it was published. The paper sparked a sweeping shift in global approaches to pain management and breastfeeding guidance for new mothers.

The Lancet, a leading medical journal, has now added an “expression of concern” to the 2006 case report after “new allegations of falsification of toxicological data, authorship issues, and ethical concerns” were flagged to the journal on Jan. 20. The move follows the recent publication of a year-long New Yorker investigation into the highly criticized paper, on top of years of Canadian media coverage.

Though outside researchers say the paper has long been debunked — and two other medical journals have already retracted similar versions — the case study has already been incredibly influential, leading to government warnings, changes in medication labelling, shifts toward the use of more potent and addictive forms of opioids, and untold numbers of women being told to choose between a common form of postpartum pain relief and safely breastfeeding their newborns.

The Lancet case study focused on the poisoning of an infant in Ontario in 2005, and purported that the baby boy’s mother had been prescribed Tylenol 3 and passed a deadly amount of morphine to her son through her breast milk.

The combination drug, commonly given for postpartum pain management, contains both acetaminophen and codeine, a mild opioid that gets partially metabolized into morphine inside the body. (Some individuals, including the woman in the case study, are genetically predisposed to converting codeine faster, and in larger amounts.)

For years after its publication, author Gideon Koren — the once-revered founder of the shuttered Motherisk drug testing lab — insisted the case showed maternally ingested codeine can be deadly for breastfeeding infants, despite mounting concern over Koren’s interpretation and questions from other scientists about its plausibility. 

Koren has long been in the spotlight amid a slate of allegations of flawed or falsified study findings and a series of scandals surrounding the Motherisk lab. 

The former facility at the Hospital for Sick Children (SickKids) in Toronto initially gained worldwide attention for using hair strands to test for drug and alcohol use in mothers, but its testing methods were deemed “inadequate and unreliable” by an independent provincial review in 2015. 

Even so, the lab’s discredited tests were used in at least eight criminal cases and thousands of child protection cases — in many instances leading to the removal of children from their families — as the Toronto Star reported in 2017.

The Motherisk lab was shut down in 2019, and Koren agreed to relinquish his medical licence in Ontario that same year. He has not yet responded to CBC News’ request for comment. 

Many long-time critics maintain that one of his most influential findings, from the 2006 case study in the Lancet, is flat-out impossible and should be fully retracted. 

“In [Koren’s] telling, it was a fluke of genetics. Mum was taking codeine. She was turning it into morphine very efficiently. It was going to breast milk, and that's how the baby died,” recalled David Juurlink, a well-known Canadian pharmacologist, toxicologist, and drug safety researcher. “And I believed that narrative for a few years.”

But it wasn’t long before Juurlink and others soon became unsettled by the study’s stunning result. Since then he’s raised alarms, saying the report falls apart under scrutiny.