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10-10-2019 | Rheumatoid arthritis | News

Dose of corticosteroid key to preterm birth risk in RA

medwireNews: Women with rheumatoid arthritis (RA) should avoid medium to high levels of oral corticosteroids (OCS) during early or late pregnancy, say researchers who found an association with increased risk for preterm birth.

Lower doses, however, were not significantly associated with preterm birth, report Kristin Palmsten (HealthPartners Institute, Minneapolis, Minnesota, USA) and colleagues in Rheumatology, which questions the thinking that that there is “an increased risk of [preterm birth] or shorter gestational length following any OCS use during pregnancy.”

Among 250 women with RA from the MotherToBaby Pregnancy Studies (2003–2014), 15 received a high average cumulative dose of OCS of 2208.6 mg prednisone equivalent during the first 139 days of their pregnancy. Their risk for preterm birth was a significant 4.77 times higher than that for 270 women with RA who did not receive corticosteroids.

The 122 women who received a medium average cumulative corticosteroid dose of 883.0 mg were also a significant 1.81 times more likely to have a preterm birth, whereas the 117 women who received a low cumulative dose of corticosteroids – mean of 264.9 mg – had a 1.38-fold increased risk that was not significant.

Corticosteroid use after 139 days of pregnancy was also investigated, based on a daily dose to allow for different lengths of pregnancies.

A high daily corticosteroid dose of 10 mg or above, taken by 141 women, was associated with a 2.45-fold greater risk for preterm birth compared with no OCS exposure.

But, as was seen in early pregnancy, a low daily corticosteroid dose (less than 10 mg) taken by 177 women after day 139 of pregnancy did not significantly increase the risk for preterm birth.

Interestingly, the researchers did not observe an association between the use of other RA medications – biologic and nonbiologic DMARDs – and the risk for preterm birth.

High preterm birth rates among women exposed to medium or high levels of corticosteroids may not be caused directly by the corticosteroids, emphasize Palmsten et al, who suggest an increase in subclinical intrauterine infection among women taking high doses of corticosteroids as a possible cause.

But for OCS use in general, they conclude that “the lack of a clear positive association between low OCS dose, [biologic]-DMARDs, and [nonbiologic]-DMARDs and [preterm birth] is reassuring for women who are able to manage RA with low OCS doses and DMARDs during pregnancy.”

By Hannah Kitt

medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group

Rheumatology 2019; doi:10.1093/rheumatology/kez405

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