After studying almost 2 million children, Danish researchers have found that moms with rheumatoid arthritis (RA) are prone to giving birth prematurely. Moreover, the Danish study showed that not only were mothers with RA having their babies earlier, but they were also having babies with a lower average birth weight. 

Premature birth is now the leading cause of death for children younger than 5 worldwide. While many risks for premature birth are well established, the link between prematurity, low birth weight, and rheumatoid arthritis is a relatively new find in the medical community.

Learn More About Arthritis During Pregnancy: Symptoms, Treatment, and Remission »

OBGYNs Should Look Out for RA Symptoms in Pregnant Patients

The results of the study, published in Arthritis & Rheumatology, showed that babies born to mothers with RA were about 3 ounces lighter on average than their counterparts. It also concluded that babies whose moms had RA were about 48 percent more likely to be born prematurely. 

Doctors don’t know precisely why mothers with RA sometimes deliver early. The Danish study on birth weight, prematurity, and rheumatoid arthritis only proved a link between RA and these outcomes, not that RA is the cause, per se.

In a statement to the press, Ane L. Rom, M.P.H., who led the study at Copenhagen University Hospital, said, "Obstetricians should be aware of the increased risk of preterm birth in women with RA and among those with preclinical signs of the disease."

Know the Numbers: Rheumatoid Arthritis Statistics »

What Other Issues Do Pregnant Women with RA Face?

Women with rheumatoid arthritis and similar illnesses can often have a safe and normal pregnancy. However, as with many chronic illnesses, there are specific risks and precautions involved with pregnancy in a patient with RA. 

There are sometimes concerns about pregnancy among RA patients because of the kinds of drugs used to treat the disease. Many doctors advise that a patient stop taking certain medications during pregnancy, which can in turn worsen RA symptoms, making pregnancy even more physically difficult for the mother.

Keep Reading: Oh, Baby! Could Your Child’s Genes Increase Your Risk of Rheumatoid Arthritis? »

In fact, some RA patients of childbearing age choose not to have children at all — or they may not have as many kids as their healthier peers. Mary Judge of Rochester, New York, who lives with rheumatoid arthritis, explains, “I have chosen not to have children because I could never be the mother I want to be because of RA. I'm also concerned how my body will respond after having a baby. I am also concerned the disease will progress quickly, which I've seen happen to a few women with RA after giving birth.”

A 2006 study on RA and childbearing decisions showed that women who were diagnosed with rheumatoid arthritis prior to pregnancy reported fewer pregnancies and fewer children overall.

There is some good news, though, for mothers-to-be who live with RA: According to several studies, about two-thirds of RA patients experience a significant decrease in disease activity during pregnancy. However, many flare up again after delivery. Doctors have yet to discover why.