The Journal of Clinical Toxicology
published the findings on April 30. Of those 15,608 babies, all born in the province of Ontario between 1998 and 2008, half, 7,804, had mothers who were prescribed medication with codeine for postpartum pain within 7 days of giving birth. The other group of babies, an equal number, had mothers not prescribed codeine.
Conversion of codeine in liver
The liver converts codeine into morphine and the concern had been that the amount of morphine converted and passed into breast milk could harm the baby, even cause death. But Dr. David Juurlink, the lead author of the study, said results
show the amount does not harm baby.
"The amount of morphine present in breast milk is very, very small," Dr. Juurlink said. "Even if the baby was ingesting large amounts of breast milk, the amount of morphine they would ingest would be somewhere between 25 and 50 times lower than the newborn might actually be given to treat pain. It's very difficult to argue convincingly that the amount of morphine that a child can ingest through breast milk is enough to be dangerous."
Likelihood of hospitalization, harm: no increase
Babies in the study were followed for 30 days following their birth and it was found that those who had mothers who were prescribed medication with codeine had no more likelihood of being readmitted to hospital in that time than babies who had mothers who were not.
They also looked to see if babies with mothers who breastfed them after having been prescribed medication with codeine were more likely to be taken to hospital to be resuscitated or for dehydration and found they were not; nor were they more likely to be taken to emergency in an ambulance. They also discovered that babies breastfed by a mother who'd been prescribed codeine were no more likely to die.
The researchers say they cannot be sure, however, how many of the women actually did breastfeed, nor can they be sure how many of them actually took the codeine they were prescribed. Nonetheless they find their results to be meaningful.
"Over a 10-year period, we found no evidence that the prescription of codeine to women following delivery was associated with various measures of neonatal harm, including death or hospitalization," Juurlink said. "While these results do not support the prescribing of codeine generally, they do suggest that serious neonatal harm is highly unlikely when the drug is prescribed to women following delivery."