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Pregnancy puts extra strain on the immune system in women with arthritis and lupus
New research shows how the immune system actually behaves throughout pregnancy – cell by cell. In some women, these differences persist even after childbirth.
During pregnancy, the immune system faces a difficult balancing act. It must accept the growing foetus, which carries genetic material from both parents, while continuing to protect the mother against infections.
For most pregnant women, this happens without any problems.
However, for women with autoimmune diseases such as rheumatoid arthritis and lupus, pregnancy places extra strain on the immune system.
This can lead to an elevated risk of pre-eclampsia, premature birth, and miscarriage.
The immune system – cell by cell
Autoimmune diseases vary greatly, and patients react differently to both the disease and the treatment. Many people have to try several medications before finding one that works for them. That's why there is a great need for biological markers that can enable more personalised treatment, including during pregnancy," says Hilde Julie Tokle Lien, a researcher at NTNU’s Department of Clinical and Molecular Medicine.
Lien recently investigated how the immune systems of pregnant women with rheumatoid arthritis and lupus actually behave during pregnancy – cell by cell.
If left untreated, these diseases react very differently to pregnancy. Women with rheumatoid arthritis often experience an improvement, while women with lupus are more likely to experience worsening symptoms.
To understand why, Lien worked with a team of different experts, such as immunologists, doctors, and nurses. Together, they used advanced methods to study gene activity in individual immune cells.
The team also developed a new method that can be used in future research.
Need for follow-up in the postnatal period
The initial results reveal clear differences in the immune systems of pregnant women with lupus, pregnant women with rheumatoid arthritis, and healthy pregnant women. One key difference is which types of immune cells are most common.
This occurs even though the women receive excellent follow-up and their disease activity changes very little during pregnancy.
In women with lupus, the differences remain even after childbirth.
“This emphasises the need for close follow-up during the postnatal period. This is a phase that has traditionally received less attention in rheumatological treatment,” explains Lien.
Important to continue taking medication
Lien and her team are now investigating whether the differences are caused by changes in gene activity or by changes in how many different types of cells are present.
They are also studying why people with the same diagnosis can have such different symptoms, and what causes their disease activity to change.
“Internationally, there's still considerable variation in the use of medication during pregnancy. Although we know that untreated disease generally poses the greatest risk, many women are reluctant to take medication while they are pregnant. It's important to continue taking the medication during pregnancy” says Lien.
References:
Lien et al. Identifying cell type and gene expression changes in pregnant women with rheumatoid arthritis and systemic lupus erythematosus, Doctoral thesis at NTNU, 2025.
Pedersen et al. 'Decoding the cytokine signatures of pregnancies with systemic lupus erythematosus and rheumatoid arthritis', Frontiers in Lupus, 2025. (Summary)
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