Pregnant women with well-controlled juvenile idiopathic arthritis and rheumatoid arthritis, and who discontinue treatment with TNF inhibitors prior to week 20 of pregnancy, do not experience worsening of their disease, a new study shows.

The study, “Discontinuing TNF-inhibitors before gestational week 20 in well-controlled rheumatoid arthritis and juvenile arthritis is not associated with a disease worsening in late pregnancy,” was published in the journal Arthritis Rheumatology.

For women with chronic inflammatory arthritis who become pregnant, stable and inactive disease is important for maternal and fetal health. This often is achieved through the use of treatment with medications. However, some women may discontinue treatment during pregnancy if their symptoms improve or due to concerns their medicine may harm the fetus.

TNF (abbreviation for tumor necrosis factor) is a pro-inflammatory molecule that is elevated in patients with inflammatory conditions such as arthritis.

In recent years, several studies have shown that the use of TNF inhibitors (TNFi) during pregnancy can be safe, leading to high rates of TNFi use during pregnancy.

Depending on disease activity and discussions between the patient and physician, TNFi use can be continued, or stopped, during the course of the pregnancy. However, any treatment changes in patients with chronic inflammatory diseases can cause changes in disease activity, sometimes triggering a previously under-control disease.

In fact, studies conducted in non-pregnant patients have shown that discontinuing  a TNFi can lead to worsening symptoms in a subset of patients with rheumatoid arthritis (RA).

In pregnant patients with RA, two factors — the presence of active disease or TNFi discontinuation — are thought to be risk factors for a disease flare during pregnancy. However, there is very little data on this topic.

That’s why researchers conducted a study to investigate the patterns of continuing or discontinuing TNFi during pregnancy, and any association with changes in disease activity over the course of pregnancy in women with RA and juvenile idiopathic arthritis (JIA).

Researchers collected information about medication and disease activity (through patient-reported outcome measures) prior to gestational (pregnancy) week 20 and at gestational week 32. Researchers then analyzed the patterns of TNFi use to determine if there were correlations with disease activity changes.

In total, 490 women were enrolled in the study; 397 had RA and 93 had JIA. At the time of enrollment, disease activity was low to minimal in the majority (72.9%) of women.

Among this group, 122 (24.9%) discontinued use of TNFi before gestational week 20, 201 (41.0%) continued to use TNFi beyond week 20, and 167 (34.1%) did not use TNFi at all during pregnancy.

When looking at patients who discontinued the use of TNFi, researchers found no association between discontinuation and a clinically significant worsening of patient-reported outcome measures in the third trimester.

However, the authors said “[o]ne important caveat of this finding is the high proportion of women in this sample (72.9%) who had low disease activity at the beginning of pregnancy.” As such, these findings may not reflect possible outcomes in pregnant women who have high disease activity.

Univariate analysis (which involves the examining a single variable, i.e., TNFi use) but not multivariate analysis (which involves the analysis of two or more variables) showed that women using TNFi after week 20 of pregnancy were more likely to experience improved disease activity scores in the third trimester.

“Discontinuing a TNFi before gestational week 20 seems feasible in women with RA and JIA who enter pregnancy with well-controlled disease,” the researchers concluded.