Pregnancy is often a time of bliss, coloured by a touch of paranoia and worry about how everything will turn out, for a woman who's expecting -- but add a previous diagnosis of multiple sclerosis to the equation and it might easily compound the concern.

However, these moms should be able to rest a little easier now, thanks to a research project at the University of British Columbia.

A comparison of data for 432 women with multiple sclerosis to 2,975 women without the disease found that essentially, there were no additional risks associated with MS in terms of how the delivery went or the condition of the baby.

The study appears in Monday's edition of the Annals of Neurology, a journal published for the American Neurological Association.

"It's reassuring to women with MS who are considering to start a family that essentially there were no risks associated with MS in terms of birth outcomes," said co-author Helen Tremlett, Canada Research Chair in neuroepidemiology and multiple sclerosis.

"When we compared mothers who had MS to mothers who did not have multiple sclerosis we found that there were no differences in birth outcomes such as mean birth weight, gestational age of babies, so they weren't being born prematurely to women with MS."

The median five-minute Apgar score was the same for babies born to MS mothers and those in the comparison group, the study showed. The Apgar score assesses the general physical condition of a newborn, looking at heart rate, muscle tone, skin colour, response to stimuli and respiratory effort.

In addition, there were no additional risks of adverse delivery outcomes, Tremlett said.

"And here we were looking at things like caesarean section -- so women with MS were not at an increased risk of having a caesarean section, nor were they at an increased risk of assisted vaginal delivery," she said.

"So I think there's a positive message there, that having multiple sclerosis does not have a negative impact on birth outcomes, at least not the immediate birth outcomes."

Canada has one of the highest rates of MS in the world. The disease doesn't have a cure, and can cause a loss of balance, impaired speech, fatigue, double vision and paralysis. It typically strikes people between the ages of 15 and 40, and more women than men.

Dr. Paul O'Connor, director of the MS Clinic at St. Michael's Hospital in Toronto, was not involved in the research, but describes it as reassuring to women with MS who are contemplating getting pregnant and having a family.

He cares for 2,500 patients with multiple sclerosis, and frequently faces questions about whether pregnancy will cause a woman's disease to progress more quickly and whether there will be an impact on a baby.

"It comes up a lot because a very large proportion of MS patients have their disease begin in their 20s and 30s and nowadays, two-thirds to three-quarters of our patients are women," he said.

The study is important for two reasons, he said.

"This is a disease that happens to people when they are having families and it's of particular interest because the majority of our patients are women."

He said that for most pregnant women with MS, their disease symptoms tend to become milder during pregnancy, particularly during the second half of a pregnancy. On the other hand there is an increased risk of a relapse in the first six months after the birth of a child, he noted.

"Overall, there is no net effect of pregnancy on long-term MS outcome in affected patients."

A large Canadian study that was done previously showed that if a woman with MS has a daughter, the risk of the daughter getting MS is about four per cent, while the risk for a son is about three per cent, he said, and the risk is even lower for the children of a father with multiple sclerosis.

Tremlett said the women in this new study tended to be fairly mobile and their disability was not that advanced.

"There was a trend toward women who had higher levels of disability who have some higher probability they might have to have a caesarean section or assisted vaginal delivery, but it was not significant -- it was just a hint of a trend."

The study had one unexpected finding: the women with MS tended to have higher body mass indexes.

"So I think there are sort of two take-home messages: perhaps women with MS should be supported in terms of optimizing their weight when they're planning a pregnancy and also actually for research in the future I think it highlights ... the fact that you need to consider body mass index when investigating the pregnancy-related outcomes in MS," Tremlett said.