There has been a five-fold increase in the use of antinausea medicines during Aotearoa New Zealand pregnancies, a University of Otago – Ōtākou Whakaihu Waka-led study has found.
Published in the Australian and New Zealand Journal of Obstetrics and Gynaecology, the research used anonymised national health data to review the prescribing patterns in 1.37 million pregnancies from 2005 to 2019.
In 2005, 4.1 per cent of pregnant individuals in Aotearoa used an antinausea medicine in their first trimester of pregnancy; by 2019 use had increased to almost 20 per cent.
Dr Sarah Donald
Co-author Dr Sarah Donald, of Otago’s Department of Public Health, Dunedin, says nausea and vomiting during pregnancy is very common, but the substantial impact it has on affected individuals has historically been under-recognised and under-treated so the increase is not surprising.
The most-commonly dispensed antinausea medicine was metoclopramide, with exposure rising from 3.1 per cent to 12.4 per cent of pregnancies over the study timeframe.
Use of another medicine, ondansetron, increased from almost no use (0.1 per cent) to 9.1 per cent.
“We were amazed at how quickly the use of ondansetron has become common during pregnancies here in New Zealand,” Dr Donald says.
Ondansetron is a very effective antinausea medicine that was developed for treating nausea caused by cancer treatments. However, it has not been approved to treat nausea in pregnancy and such use is considered ‘off-label’.
“Most clinical guidelines from the study period recommended ondansetron only if other antinausea medicines had been ineffective. But what we saw was, over time, its use as a first-line treatment also increased.
“Loosening of prescribing restrictions over time, and the fact that it comes in an easy-to-take dissolvable tablet, have probably contributed to its rising popularity for treating nausea in pregnancy. Newer guidelines now recommend ondansetron as one option for first-line treatment in those with moderately severe symptoms.”
Dr Donald says nausea and vomiting in pregnancy affects up to 70 per cent of pregnancies and, as with any medicine used during pregnancy, the safety of antinausea medicines need to be considered.
Several previous studies have suggested that ondansetron exposure during the first trimester of pregnancy may be associated with a very small increase in the risk of birth defects such as heart defects and cleft lip/palate. However, other studies have not found increased risk, and the evidence overall is unclear.
“With increasing ondansetron exposure in early pregnancy, further information on its safety would be helpful to better guide treatment decisions,” Dr Donald says.
This study is part of a larger project funded by the Health Research Council. The research team is currently undertaking work investigating whether early pregnancy ondansetron use is associated with several adverse pregnancy outcomes.
Publication:
Dispensing of Antiemetics During Pregnancy in Aotearoa New Zealand, 2005–2020
Sarah Donald, Katrina Sharples, Dave Barson, Karyn Maclennan, Leanne Te Karu, Diana Phone, Hedwig van Asten, Michael Stitely, Lianne Parkin
Australian and New Zealand Journal of Obstetrics and Gynaecology
https://doi.org/10.1111/ajo.70157
