An intriguing new RA study links dad’s genes to mom’s health.

A new study has given birth to a groundbreaking theory in the rheumatology community. This study shows that a child’s genes, including those inherited from the father, may affect a mother’s risk for rheumatoid arthritis (RA). In fact, fetal cells that may carry certain genes that increase RA risk can thrive in a mother’s body long after she gives birth.

Doctors have long known that women are at far greater risk of developing RA than their male counterparts. This suggests that factors exclusive to female reproduction may be involved. Now, we’re learning just how pregnancy could relate to RA.

Perhaps moms-to-be should take their husband’s family health history a little more seriously, since it could affect their own health in ways never understood before.

Learn About RA Risk Factors: Is It Hereditary? »

“During pregnancy, you’ll find a small number of fetal cells circulating around the mother’s body, and it seems that in some women, they persist as long as several decades. Women with rheumatoid arthritis are more likely to have this persistence of fetal cells, known as fetal microchimerism, than women without the condition, suggesting that it is a potential risk factor for the development of rheumatoid arthritis,” said graduate student researcher Giovanna Cruz from the University of California, Berkeley, in a press release.

Cruz believes that human leukocyte antigen (HLA) genes, which regulate the immune system, may be the culprits. In the study, researchers found that having children with certain HLA genes that are considered high-risk for rheumatoid arthritis — and that were inherited from the father — increased the mother’s risk of later developing RA.

Proteins that these genes encode could stimulate an autoimmune reaction in the mother, causing her immune system to mistakenly target proteins produced by the fetus as a threat and beginning the autoimmune process of RA without her knowing. Since fetal cells can remain in a woman’s body for years after giving birth, this autoimmune response could persist well past pregnancy and childbirth.

Read More: Have Researchers Found a Way to Halt Rheumatoid Arthritis Progression? »

Dr. Scott Zashin, a fellow of the American College of Physicians and the American College of Rheumatology, simplified this theory, explaining, “The cause of RA is unknown. This study speculates that the persistence of fetal cells in some women during and after pregnancy is a potential trigger for RA. If that is true, the cells act as a foreign antigen that reacts with antibodies of the mother causing inflammation in the joints. Once this inflammatory cascade begins, patients may develop RA.”

Some patients believe that childbirth can affect rheumatoid arthritis in other ways, too. Patient Sarah Rabideau from Morrisville, North Carolina, said, “My RA was under control prior to giving birth. After having my son I stopped responding to medications.” Her condition got so bad that she eventually had to stop working and buy a single story home to accommodate her needs.

As with many areas of life, pregnancy, childbirth, and child rearing may be more difficult for those who live with RA than for those who do not. However, there are always resources available through your rheumatologist and advocacy organizations to help make the transition to motherhood a smooth one, even with a chronic condition.