That view has since proved demonstrably incorrect, thanks to studies such as one published in the New England Journal of Medicine in 1998 showing that relapse rates actually decline during pregnancy, especially in the third trimester, while increasing in the first three months postpartum and then returning to the pre-pregnancy level.
And this seems to have had an impact on birth rates among women with MS. According to a study last year in Neurology, pregnancy rates among women with MS increased from 7.91% in 2006 to 9.47% in 2014, while the rate among women without MS and with pregnancy decreased from 8.83% to 7.75%
Preliminary results from a study presented at the annual meeting of the American Academy of Neurology earlier this year, using data from the Kaiser Permanente Southern and Northern California databases spanning 2008 to 2016, indicated that women with MS who became pregnant did not experience increased risk of relapse after pregnancy.
In this study, the annualized relapse rate was 0.39 before pregnancy. The rate plummeted to about 0.07-0.14 during pregnancy, and then rebounded to 0.27 after birth -- still slightly lower than the pre-pregnancy rate. By four to six months after birth, the rate had returned to the pre-pregnancy level, at 0.37.
"I tell patients they should expect the same amount of relapse activity overall in the year they are pregnant and post-partum, but it's just going to be distributed so that its lower in the third trimester and higher in the postpartum period," said Nancy L. Sicotte, MD, director of the Multiple Sclerosis and Neuroimmunology Center at Cedars-Sinai Medical Center in Los Angeles. "But there are no long-term negative consequences, other than a typical post-partum relapse."
However, pregnancy for women with MS "should be a planned process," she said, with pre-pregnancy counseling that includes special management of these patients' medications.
Over the years the FDA has approved a number of disease-modifying therapies for MS, ranging from injectable medications ranging from glatiramer acetate (Copaxone) to oral medications such as fingolimod (Gilenya) and infused agents such as natalizumab (Tysabri).
"None of these medications are advised to be used during pregnancy, and if planning to become pregnant you need to go off of your medications," said Sicotte, adding that in the case of two drugs -- fingolimod and natalizumab -- the process is a little more problematic.
Studies have shown that these drugs are associated with what is called a "rebound syndrome" in patients with MS after they've ceased taking the drug. This can be described as disease activity well above the level one would have expected based on a patient's disease activity prior to the start of treatment.
For example, a case report and literature review presented last year concluded that "MS rebound after discontinuation of fingolimod can occur regardless of age, whether relapsing or progressive, even after short treatment duration."
So these drugs can put women at risk for increased disease activity, despite the fact that pregnancy is partially protective in MS patients in the third and even second trimesters, explained Sicotte. "We want this to be a managed process."
Because of its relative safety, some doctors will prescribe glatiramer acetate during pregnancy. According to a review in Biomedicines, women who are considering pregnancy and are taking fingolimod or natalizumab should be counseled regarding the risk of rebound activity, and switching to a safer medication such as glatiramer acetate or interferon-beta should be considered.
But, while relapses may diminish during pregnancy, they still occur. "The good news is that we can treat them and for most periods during pregnancy it is safe to use high dose steroids, like we typically do for a typical relapse," said Sicotte. "We are able to give them a treatment that will speed up recovery of the symptoms and so it is usually able to be pretty well managed if they do have a relapse during pregnancy."
One review in 2016 indicated that methylprednisolone is the preferred drug for treating relapse in pregnancy because it is metabolized before crossing the placenta; dexamethasone, on the other hand, does cross the placenta with minimal metabolism and should be avoided.
For pregnant women experiencing symptoms related to their disease, many medications should not be used at their usual doses, Sicotte said, "although lower doses of many of these meds have been shown to be reasonably safe."
Many times clinicians will use non-medicinal methods for managing symptoms, she added, and they should work closely with neurologists "to find the best combinations of interventions to help with some of the symptoms they have with MS."
As for the actual delivery, Sicotte explained that there once was a belief, "based on little data," that spinal block during delivery could be dangerous to MS patients. "But there is no evidence that there is any long term consequence in using that type of anesthesia," she said.
"Our goal as clinicians is really to help women live their best lives and recognize that many of the things they may have thought about what having MS means to them, are not really true," Sicotte said. "Many, many folks with MS have very active lives, and can do the things they want to do, and that includes having a baby."
Sicotte reported no relevant financial interests.