Stopping asthma drugs during pregnancy linked to premature births and small babies

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

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Prescriptions of asthma medicines before or during pregnancy have been linked to a higher risk of premature birth and small birthweight babies, according to UK research, but the study found that this was particularly the case if prescriptions were stopped during pregnancy. The authors say prescriptions records could be used to identify the women who need extra help and support.

Journal/conference: PLOS ONE

Link to research (DOI): 10.1371/journal.pone.0242489

Organisation/s: Swansea University, UK

Funder: This paper was developed from the EUROmediCAT project, and uses the cohort identified in that project. The analyses presented here were completed outside the funded period. Financial support for the EUROmediCAT study was provided by the European Union under the 7th Framework Program [grant agreement HEALTH-F5-2011-260598]. Start date: 1 March 2011. Duration: 48 months. Coordinator: Prof. Helen Dolk, University of Ulster. Further information can be found at The paper is based on data in the all-Wales SAIL databank, which is supported by UK Research and Innovation funding to Swansea University through an Administrative Data Research Centre grant (2018-2021), project reference: ES/S007393/1, Principal Investigator: Professor David Ford. The funder played no part in the study or production of the paper

Media release

From: PLOS

Maternal asthma medications may be associated with premature births and small birth weight in infants

Prescriptions for asthma medicines, whether continued or discontinued during pregnancy, are associated with premature births and small birth weight, according to a new study published this week in the open-access journal PLOS ONE by Sue Jordan of Swansea University and colleagues.

The prevalence of asthma in pregnancy has increased worldwide in recent years and these is no consensus on the effect of asthma or asthma medications on perinatal outcomes. However, it is known that medicines prescribed for asthma can cross the placenta.

In the new study, researchers analyzed all births in Wales after 24 gestational weeks between January 2000 and December 2010, with associated maternal prescription data (117,717 births). Exposure to any asthma medication was defined as the woman having been prescribed at least one asthma medicine in the three trimesters of pregnancy. Pregnancies terminated for fetal anomalies, infants with congenital anomalies, pregnancies that were not singletons, and those exposed to other drugs or substances associated with perinatal outcomes were excluded.

Prescriptions for asthma were associated with birth before 32 weeks gestation (aOR 1.33, 95%CI 1.10-1.61) and birthweights below the 10th percentile (aOR 1.10, 95%CI 1.03-1.18). Moreover, the discontinuation of asthma medicine during pregnancy was associated with both birth before 32 weeks (aOR 1.53, 95%CI 1.11–2.10) and birth before 37 weeks gestation (aOR 1.22, 95%CI 1.06–1.41). Stillbirth was also more prevalent among women prescribed asthma medicines than the unexposed population (aOR 1.56, 95%CI 1.21–2.00), particularly if the medicines had been discontinued during pregnancy (aOR 1.91, 95%CI 1.29–2.82). The authors conclude that increased monitoring, targeted support and active asthma management are needed before, during and after pregnancy.

The authors add: “This analysis of prescription records for over 100,000 pregnancies found that women who stopped their asthma medicines during pregnancy were at increased risk of preterm birth and not breastfeeding at 6-8 weeks, whereas women who continued with their inhaled corticosteroids were at lower risk. Prescriptions records could be used to identify the women who need extra help and support.”



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