Study reveals safety of MS drugs during breastfeeding in child's early years of life

Certain medications for multiple sclerosis (MS) called monoclonal antibodies, taken while breastfeeding, may not affect the development of a child during the first three years of life, according to a preliminary study released today, March 4, 2024. The study will be presented at the American Academy of Neurology's 76^th Annual Meeting taking place April 13–18, 2024, in person in Denver and online. The study examined four monoclonal antibodies for MS: natalizumab, ocrelizumab, rituximab and ofatumumab.

MS is a disease in which the body's immune system attacks myelin, the fatty white substance that insulates and protects the nerves. Symptoms may include fatigue, numbness, tingling or difficulty walking.

Most monoclonal antibody medications for multiple sclerosis are not currently approved for use while a mother is breastfeeding. Yet MS can develop during the childbearing years of life. Since the risk of MS relapses increases after giving birth, some mothers may need or want to restart these therapies, so it is important to determine whether these medications, through breast milk, have a negative impact on a child's development."

Kerstin Hellwig, MD, study author of Ruhr University in Bochum, Germany

For the study, researchers used the German MS and Pregnancy Registry to identify 183 infants born to mothers taking monoclonal antibodies while breastfeeding. Of this group, 180 had mothers with MS and the three had mothers with neuromyelitis optica spectrum disease (NMOSD). NMOSD is also a demyelinating disease, but it is rare and specifically affects the optic nerve, spinal cord or brain. 

The infants were compared to another 183 infants, matched for exposure to MS medications shortly before or during pregnancy, born to mothers with the same diseases who did not take monoclonal antibodies while breastfeeding.

Of those exposed to MS medications, 125 were exposed to natalizumab, 34 to ocrelizumab, 11 to rituximab and 10 to ofatumumab. Two infants were first exposed to natalizumab and then ocrelizumab. One infant was exposed to rituximab and then ocrelizumab.

The first exposures to the medications through breastfeeding ranged from the day a child was born to the ninth month of life. Infants were breastfed for an average of five-and-a-half months while their mothers took these medications.

For all infants, researchers then examined the number of hospital stays, antibiotic use, developmental delays such as problems with social and fine motor skills and delayed speech development, and the infants' weight at follow-up visits during the first three years of life.

After comparing infants exposed to the medications to infants not exposed, researchers found no differences in their health or development.

"Our data show infants exposed to these medications through breastfeeding experienced no negative effects on health or development within the first three years of life," Hellwig said.

A limitation of the study was that only about a third of the infants were followed for the full three years. Therefore, Hellwig said, the results for the third year of life are less meaningful than for years one and two.