Ellen Phiddian
Cosmos science journalist
Opioids like morphine and codeine are commonly prescribed after giving birth to alleviate pain – particularly after a caesarean section.
But these opioids pass into breast milk in small amounts, which has led to concerns that the drugs might be dangerous to infants.
A study published in The British Medical Journal has challenged this fear, showing no greater risks to infants if their mothers are prescribed opioids.
The researchers drew on Canadian hospital records to examine data from mothers who had given birth to single children in Ontario hospitals from September 2012 to March 2020, and been discharged within a week.
This totalled 865,691 mother-infant pair records. After excluding records, mostly because of missing data, they had 85,852 records for mothers who’d been prescribed opioids and 538,815 mothers who hadn’t.
Four in five of the mothers who’d been prescribed opioids (81%) had delivered via caesarean section.
The researchers matched each mother who’d been prescribed opioids with a single record in the non-opioid group – that is, a mother with similar health, demographics, socioeconomic status, and delivery conditions.
This gave them a control group with very similar features to the opioid-prescription group.
They then examined records for the infants’ first 30 days, checking for hospital readmissions, emergency department visits, admissions to neonatal intensive care, and deaths.
They found very little difference between the opioid group and the non-opioid group.
In both groups, 3.5% of infants were readmitted to hospital within 30 days of birth.
Read more: Caesarean-born babies still get their microbe fix from mum
There wasn’t any difference between the opioid-prescribed group and the non-opioid group in terms of serious outcomes or admission to neonatal intensive care. No infant death happened in either group.
The only slight difference they could find was that infants in the opioid prescribed group were 0.41% more likely to be taken to the emergency department in the month following birth.
In their paper, the researchers point out that “millions of mothers in North America and hundreds of thousands of new mothers are prescribed opioids after delivery each year”, but there’s no evidence that these prescriptions have led to opioid toxicity.
That said, they still point out that they don’t have data on whether the mothers took the opioids they were prescribed – nor do they know if the babies were breastfed, although 90% of mothers in Ontario do breastfeed their babies in the first month of life.
Nevertheless, they say their study adds to the body of evidence that opioids after birth don’t cause any harm to the infant.
“This study found no association between maternal opioid prescription after delivery and several adverse infant outcomes, including death,” conclude the authors.
“Although we endorse caution in short term postpartum opioid use in selected mothers, clinicians and parents should be reassured that infants are at low risk of harm.”