Preterm birth risk with OCS for asthma depends on timing and exposure

4 minute read

A study finds an association between oral corticosteroids and pregnancy outcomes, but this may be confounded by the effects of asthma itself, NAC warns.

The timing and dose of oral corticosteroids used during pregnancy affects the risk of preterm birth, according to a study of Californian women with asthma or two autoimmune diseases.

Oral corticosteroids (OCS) are used to manage acute flare-ups in severe asthma and as an anti-inflammatory treatment for autoimmune conditions, though they have been linked to poor pregnancy outcomes for mothers and their babies. Their use is associated with preeclampsia, preterm birth (PTB) and low birth weight.

Still, there is limited information available about the effect of dose and timing of OCS use during pregnancy, especially among women with asthma, which affects nearly 13% of pregnancies in Australia.

Seeking to inform treatment decisions, researchers have now reported an increased risk of preterm birth with higher doses of OCS in early pregnancy for women with asthma.

The cohort study compared pregnancy outcomes in more than 22,000 women with asthma, nearly 1,200 women with systemic lupus erythematosus and another 470 with inflammatory bowel disease.

The women’s exposure to OCS was estimated using dispensing data from the California Medicaid Program, a health insurance program for low-income individuals in California. Linking the health records of mothers and their babies, the researchers found that for women with asthma, higher doses of OCS early in pregnancy – but not later – increased the risk of an early delivery, three weeks or more before the baby’s due date.

Early pregnancy was defined as before day 140.

The researchers measured exposure in two ways. For the first 139 days of pregnancy, women were grouped by the low, mid-range or high cumulative dose they had received. After 140 days until birth, OCS exposure was calculated using daily doses of <10, 10 to 20 or >20 prednisone-equivalent mg/day and adjusted for the length of their pregnancy.

After adjusting for covariates, PTB were 1.5 times more likely for women with asthma who had received high doses of OCS early in pregnancy than women who did not receive any OCS at all.

“We observed very high absolute risks for PTB among women with asthma, ranging from 14% in women with no OCS to 33% for the highest OCS doses,” the authors wrote.

Women with SLE had an increased risk of PTB with higher OCS doses early on and later in pregnancy.

Dr Kristin Palmsten, an epidemiologist at the HealthPartners Institute, Minneapolis, and lead author of the study, said the results should help patients and healthcare providers make decisions about using OCS treatment during pregnancy.

“Our study contributes more nuanced preterm birth risk information regarding oral corticosteroid dose and gestational timing of use for women with asthma, SLE, and inflammatory bowel disease,” she said.

Other factors affecting pregnancy outcomes, including the mother’s age and smoking during pregnancy were taken into account, along with proxies of disease severity and symptom control, such as emergency department visits or admissions.

Nevertheless, the National Asthma Council Australia, which provides comprehensive guidelines to managing asthma during pregnancy, notes that separating the outcomes of using OCS during pregnancy from the effects of any asthma flare-ups necessitating such treatment is difficult. Exacerbations and moderate-to-severe asthma are likewise associated with preterm births.

This underscores the benefit of active management of asthma during pregnancy to control symptoms and prevent exacerbations, to reduce a woman’s risk of preterm delivery.

In the Californian study, no association was observed between the use of asthma preventer therapies and preterm births.

“Our findings support the treatment goal of controlling asthma symptoms during pregnancy and are reassuring for women who can manage asthma during pregnancy with lower oral corticosteroid doses and controller therapies,” the authors concluded.

The National Asthma Council Australia recommends regular four-weekly asthma reviews for women during pregnancy and the use of preventer medications, if indicated, just as for other adults.

J Allergy Clin Immunol Pract 2020, 11 Aug

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