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Inhaled corticosteroids (ICSs) for asthma are not associated with increased risks for either mother or baby, a large cohort study has found.
Publishing their findings in JAMA Network Open on 24 August 2026, researchers analysed data from 6,105 pregnancy outcomes in South Korea between 1 January, 2009 and 31 December 2023, which were gathered from South Korea’s National Health Information Service and its ‘National Health Screening Program for Infants and Children’.
Participants were included in the study if they had a recorded diagnosis of asthma and at least two prescriptions for ICS within the 180 days prior to the estimated date of their last menstrual period. In the final study cohort, there were 2,108 pregnant women who continued ICS use and 3,997 women who discontinued it.
During the study, women who continued ICSs during pregnancy were identified by having had at least 1 ICS prescription during the first trimester. “[This] represents a clinically critical window during which women often become aware of pregnancy and may discontinue or modify medication use,” the study authors said.
There were no statistically significant differences in maternal outcomes between the ICS continuation and discontinuation groups, the study results revealed. The risks analysed were preeclampsia, gestational diabetes, obstructed labour, antepartum haemorrhage, premature rupture of membranes risk and preterm birth.
The study results also showed no statistically significant differences in neonatal outcomes, which included the risk of hypoxia or asphyxia, low birth weight and congenital malformation.
International guidelines recommend continuing ICS maintenance therapy during pregnancy to preserve asthma control, while multiple studies have suggested that ICS use during pregnancy is not associated with increased risk, the study authors noted.
However, they added that many women with asthma still discontinue ICS during the early stages of pregnancy.
“[The findings] support continuing ICS therapy during pregnancy when clinically indicated while highlighting the importance of individualised risk assessment and maintaining asthma control in accordance with established clinical guidance,” the study authors continued.
Darush Attar-Zadeh, honorary clinical fellow respiratory pharmacist at North West London Integrated Care Board, commented: “Asthma is a condition involving inflammation of the airways and, if it is not well controlled, it can be serious and even fatal. During pregnancy, there are many hormonal and physical changes, so it is particularly important that asthma remains well controlled.
“ICSs target inflammation directly in the airways and — particularly at low doses — have far fewer systemic effects than oral corticosteroids. The benefits of continuing prescribed treatment usually outweigh the risks of stopping it and having poorly controlled asthma.
“NICE [National Institute for Health and Care Excellence] guidance advises that ICSs can be used as normal during pregnancy. It also recommends that people with asthma have a review during early pregnancy and in the postpartum period.”
Attar-Zadeh added: “In my experience, some patients are understandably worried about using medicines during pregnancy and may have questions about whether their inhalers are safe. They should be advised not to stop or change their treatment without speaking to their pharmacist, asthma nurse or doctor.
“Inhaler technique should be optimised to ensure effective delivery to the airways, and the RightBreathe website can be used to illustrate the dose of corticosteroid delivered by their inhaler.”
Ian Jarrold, deputy head of research and innovation at Asthma + Lung UK, said: “It’s very reassuring to see that the continued use of ICSs in early pregnancy was not associated with any adverse maternal or neonatal outcomes in this study. Pregnancy can affect and change the way women experience asthma in many different ways, which can affect how well it’s controlled.
“This robust study supports current guidelines around ICS therapy during pregnancy and highlights the importance of individualised risk assessment while maintaining asthma control.”
