Codeine is a common active ingredient in many painkillers – including those prescribed to women right after a C-section.

However, a recent study by researchers at the University of Western Ontario indicates that codeine may actually present a danger to breastfed infants. This is contrary to what the American Academy of Pediatrics says – that codeine is compatible with breastfeeding.

Codeine itself is harmless. However, it is transformed by the body into morphine, which is the actual substance that eases the pain. The researchers discovered that some individuals have a genetic predisposition that makes their body metabolize codeine faster than normal. In lactating women, this can cause a build up of morphine in the breast milk, thus putting babies at risk of morphine overdose. This predisposition is very rare but it definitely exists and should therefore be taken into consideration when prescribing painkillers to breastfeeding women. With the increasing rates of C-section, more and more women and their babies will be put at risk.

Several cases of babies who have suffered from morphine overdose via breast milk have been reported in Canada and at least one case proved fatal. Morphine overdose leads to central nervous system depression in babies.