High rates of opioid use found in NZ pregnancies

Aotearoa New Zealand has the third highest prevalence of prescribed opioid use during pregnancy in a new multi-national study of 13 high-income countries.

Co-author of the research Dr. Sarah Donald, of the University of Otago—Ōtākou Whakaihu Waka Department of Preventive and Social Medicine, says the findings were unexpected and the risks of opioid use need to be better considered.

“Of the participating countries, only the US and Iceland had higher prescribed use. Almost 8% of pregnancies in New Zealand were exposed to an opioid, compared to only 4% in Canada and 0.4% in the UK,” she says.

“Opioid use will be influenced by local factors such as the prevalence of pain-related conditions, the organization of the health system, and approaches toward pain relief, but this between-country variation suggests it is time to take a look at the New Zealand guidelines,” she says.

The study, led by the University of New South Wales and published in journal Anesthesiology, analyzed prescription analgesic opioid use during more than 20 million pregnancies, excluding during childbirth, from the years 2000 to 2020.

It used anonymized data from Australia, New Zealand, Canada, the US, Denmark, Finland, Iceland, Norway, Sweden, the UK, Hong Kong, South Korea and Taiwan, and found use was stable, or downward trending over time in most countries.

The highest rate of use was in the US and the lowest was in the UK. Overall, the most common opioids taken were codeine and tramadol.

Use was more common in late pregnancy, and among those with lower income and higher body mass index.

Dr. Donald says use of any prescription medication during pregnancy also increased over the 20-year period.

“This general trend may reflect the increasing age of pregnant individuals, and therefore a higher prevalence of medical conditions requiring treatment, as well as growing recognition of the historic undertreatment of pregnant people.

“For opioids specifically, the drivers of increased use in pregnancy are unclear, and further research in this area would be helpful. It is reassuring, though, that of those using an opioid during pregnancy, about 80% received just one prescription.”

Co-author Professor Lianne Parkin, also of Otago’s Department of Preventive and Social Medicine, says opioids cross the placenta, exposing the fetus, and use during early pregnancy may increase the risk of certain congenital malformations.

“They can also increase the risk of adverse outcomes such as preterm birth and low birth weight, breathing problems or withdrawal symptoms in the baby after delivery, and longer-term neurodevelopmental conditions.

“These risks need to be considered when deciding whether to use opioids to treat moderate or severe pain during pregnancy.”