Rheumatoid arthritis in pregnancy associated with low birth weight and premature birth

The results of a study presented today at the Annual European Congress of Rheumatology (EULAR 2018) demonstrate that pregnancies in women with rheumatoid arthritis are associated with premature delivery and low birth weight.

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects a person's joints, causing pain and disability. It can also affect internal organs. RA is more common in older people, but there is also a high prevalence in young adults, adolescents and even children, and it affects women more frequently than men.

It is well documented that during pregnancy many women with RA 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 rejecting the foetus. However, the effect of RA in pregnant women on foetuses is less known.

"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 Dr. Yun-Chen Tsai, Division of Rheumatology, Allergy and Immunology, Chang Gung Memorial Hospital, Taoyuan, Taiwan (study author). "While these findings are important, they should not discourage women with RA from trying to conceive."

Results of this study showed that babies born to women with RA were associated with an increased chance of low birthweighti (OR 1.65, 95% CI 1.37-1.98), prematurityii (OR 1.41, 95% CI 1.13-1.68), and being small for their gestational age (OR 1.62, 95% CI 1.36-1.92). Investigators also looked for potential risks to the mother but, apart from preterm labour, no associations were found. Investigated outcomes included birth-related death, cardiovascular complications, surgical complications and other systemic organ dysfunction.

"Pregnancy in patients with rheumatoid arthritis is very complex as there are many factors clinicians and patients need to consider and limited data available," said Professor Robert Landewé, Chairperson of the Scientific Programme Committee, EULAR. "More information is needed to understand implications of the disease and treatments on both mother and foetus."

Investigators identified 845 women with single pregnancies who also had RA from over two million pregnancies within the Taiwan National Health Insurance database and birth registry between 2001 and 2012. Statistical analysis was conducted using an adjusted generalised estimating equation model to estimate the association between RA and pregnancy outcomes.