First-Trimester Miscarriages in Women with MS

Summary: Canadian researchers study first-trimester miscarriages in Canadian women with multiple sclerosis (MS). The study followed 205 women with MS and found similar rates of first-trimester miscarriages compared to the general population. These findings offer reassurance to women with MS and their healthcare providers when discussing family planning.

Details: Dr. Dessa Sadovnick (UBC) and team looked to understand the frequency of first-trimester miscarriages in women with MS compared to the general population. They established the Canadian Multiple Sclerosis Pregnancy Study (CANPREG-MS), a prospective registry of women with MS who are pregnant or trying to conceive. Unlike other pregnancy registries, this registry captures one’s entire reproductive history (pre- and post- MS diagnosis). The study collected data from 205 women with MS who were pregnant or trying to conceive, and tracked their medical records, including their use of disease-modifying therapies (DMTs).

Results:The study reported a total of 208 pregnancies of which 36 resulted in first-trimester miscarriages that were experienced by 24 women with MS. The study found the rate of first-trimester miscarriages for women with MS was 17%, which is within the expected 15%-20% range for first-trimester miscarriages for the general population in Canada.

  • Of the 24 women that had at least one first-trimester miscarriage, 21 had been exposed to DMTs. Eight of these women completed their recommended DMT washout.
  • Five women enrolled in the study had eight pregnancies end in a miscarriage after fertility treatment [intrauterine insemination (IUI), and/or in vitro fertilization (IVF)].

At the end of the study, many of the women who experienced unexplained miscarriages continued trying to conceive and went on to give birth or became pregnant. The study did not identify any MS-related risk factors for miscarriage compared with the general population. Given the size of the study, the researchers did not see an effect of individual DMTs on miscarriage, and the results do not imply that unplanned conception while exposed to DMTs is safe. Ongoing data collection will provide more information about safety on DMT use in relation to pregnancy in women with MS.

Impact: The findings of this CANPREG-MS study provide real world evidence that women with MS do not have increased rates of first-trimester miscarriages compared to the general Canadian population. These findings provide helpful information for family planning. Women who are planning to become pregnant should discuss their treatment plan with their healthcare team.


  • Article published in Multiple Sclerosis Journal on January 22, 2023 – The Canadian Multiple Sclerosis Pregnancy Study: First-trimester miscarriages in women with multiple sclerosis. Link to article –here.
  • For more information on the rationale and methodology of the CANPREG-MS study, see here.