However, the overall risk is still low and the findings won't change the management of women with lupus, said one expert.
"I wouldn't tell my lupus patients not to get pregnant," Dr Yousaf Ali, acting chief of rheumatology at Mount Sinai Hospital in New York City.
The study was undertaken to follow up on earlier, small reports that found that women with systemic lupus erythematosus (SLE) the most common form of the disease may have an excess risk of having children with an autism spectrum disorder, said lead investigator Dr Evelyne Vinet, an assistant professor in the rheumatology department at McGill University Health Centre in Montreal.
"We identified all women with systemic lupus erythematosus in a Quebec database and matched them to women who didn't have SLE, and we were able to see how many of their children were diagnosed with an autism spectrum disorder," Vinet said.
No proof of cause
About 1.4% of children born to women with lupus were diagnosed with an autism spectrum disorder, compared to 0.6% of children born to women without lupus, the study found. It's important to note that while this study found an association between lupus in women and autism in their children, it wasn't designed to prove that the mother's lupus caused the autism.
Vinet is scheduled to present the findings at the American College of Rheumatology annual meeting in San Diego.
In lupus, as with other autoimmune disorders, the body's own immune system mistakenly attacks and destroys healthy cells, damaging the skin, joints and other organs. In some cases, the brain and nervous system are affected.
Autism spectrum disorders include a group of neurodevelopmental disabilities that can range from mild, as in Asperger's syndrome, to full-blown autism. Children with autism display social problems, communication difficulties and restricted, repetitive patterns of behaviour.
Vinet said research done in mice has suggested that the rogue immune system cells that account for a mother's lupus may react with cells in the brains of her offspring.
The new study included 509 women with lupus who had 719 children and, for comparison, a group of nearly 5 900 women without lupus who had about 8 500 children.
In addition to finding that the incidence of autism disorders was doubled for children of women with lupus, the researchers also found that the autism diagnosis occurred earlier in children whose mothers had lupus. The average age was 3.8 years for children of women with lupus compared to 5.7 years for children of women without lupus.
Vinet said it's not clear why children of women with lupus would be diagnosed sooner. But the researchers hypothesize that the autism in these children may be more severe, or it may simply be that women with lupus are more vigilant about any changes in their children's health.
The researchers also controlled the data to see if pregnancy complications, such as preterm birth, gestational diabetes or being born small for gestational age, would affect the rate of autism in the children. After controlling for these factors, they found the risk of autism was slightly more than twofold for the children of women with lupus.
Ali said it would be important for these findings to be replicated in another study.
The findings shouldn't alarm women with lupus who want to become mothers, he noted.
"Lupus is a disease of young women of childbearing age, and the absolute risk of having children with an autism spectrum disorder is very small," Ali said.
Women who want to start a family should see their doctors ahead of time so they can switch medications before pregnancy if necessary (some aren't considered safe for pregnancy), Ali and Vinet said. They should also wait until their disease has been quiet for at least six months before conceiving, the doctors said.
Data and conclusions presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.
Learn more about lupus and pregnancy from the March of Dimes.