Babies born to women suffering from rheumatoid arthritis during pregnancy are likely to have low birth weight and be premature, according to researchers.

Rheumatoid arthritis is a chronic inflammatory disease that affects a person's joints, causing pain and disability and can also affect internal organs. While the condition is more common in older people, there is also a high prevalence in young adults, adolescents, and even children, and it affects women more frequently than men. The study showed that babies born to women with rheumatoid arthritis were associated with an increased chance of low birthweight, prematurity, and small size for their gestational age.

"Our results add to a growing body of evidence from different populations suggesting small but significant increases in prematurity and a decrease in birth weight in pregnancies in mothers with rheumatoid arthritis," said Yun-Chen Tsai, from the Chang Gung Memorial Hospital, Taoyuan in Taiwan.

The results, presented at the Annual European Congress of Rheumatology (EULAR 2018) in Amsterdam, showed that except premature delivery, no adverse outcomes have reported for mothers with rheumatoid arthritis. "While these findings are important, they should not discourage women with arthritis from trying to conceive," Tsai added. It is well documented that during pregnancy many women with arthritis experience improvement in their symptoms.

This is thought to be due to alterations in the body which suppress the immune system to stop the mother from rejecting the foetus. However, the effect of arthritis in pregnant women on foetuses was less known, the researchers said. For the study, the team examined 845 women with single pregnancies who also had arthritis.