The researchers identified 103 children under the age of 10 who had been treated at hospitals in Ontario for opioid overdoses between 2002 and 2015 and whose mothers had received medications, both opioids and non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen, subsidized through the province’s public drug program.

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I don't understand. If all 103 children were treated for opioid overdoses and only some of the mothers had received opioid medications, how did all of the children overdose on opioids?