First-Trimester Miscarriage Rate Similar in Women With MS and General Population

During the first trimester, women with multiple sclerosis (MS), compared with the general population, are not more likely to have a miscarriage in the first trimester, according to study findings published in the Multiple Sclerosis Journal.

Many women with MS are diagnosed during childbearing years. Although many patients wish to become pregnant, there is a lack of evidence-based data about reproduction in MS.

This study was designed to better-understand the rates of miscarriage in the first trimester in the setting of MS. Researchers from the University of British Columbia in Canada sourced data for this study from the Canadian Multiple Sclerosis Pregnancy Study (CANPREG-MS), which was a prospective pregnancy registry for women with MS. Women (N=205) with confirmed MS who were pregnant or actively planning pregnancy and lived in Canada were recruited. The first trimester was defined as 13 weeks’ gestation.

The study population comprised women mean age, 32.93 (SD, 3.89), they were diagnosed with MS at age 27.82 (SD, 5.18), and 52.68% had a pregnancy prior to enrollment in CANPREG-MS.

The overall rate of first-trimester miscarriage was 17.31% (95% CI, 12.43%-23.15%), in which 36 pregnancies from 24 women were lost in the first trimester. This rate was similar to the rate observed among the general population in Canada (15%-20%).

Among the subset of women who did not have a miscarriage while enrolled in CANPREG-MS and had a pregnancy prior to MS diagnosis, the rate of first-trimester miscarriage was 17.54%. Among the women who did not miscarry while enrolled in CANPREG-MS and had a pregnancy after MS diagnosis but before enrolling in CANPREG-MS, 46.91% had a miscarriage in the first trimester.

Among the women who had at least 1 first-trimester miscarriage during CANPREG-MS enrollment, the subset who had a pre-MS pregnancy had a rate of first-trimester miscarriage of 14.29% and the subset who had a previous pregnancy after MS diagnosis but before enrollment had a miscarriage rate of 66.67%.

The miscarriages that occurred during CANPREG-MS enrollment were unexplained (n=30), associated with fertility treatment (n=13), uterine polyps or fibroids (n=6), bicornate uterus (n=2), polycystic ovary syndrome (n=2), and chromosomal defects (n=1).

Stratified by disease-modifying therapy (DMT) exposure,

• 7 miscarriages occurred among women who were DMT naïve,
• 6 occurred after ocrelizumab exposure with a lag of 2 menstrual cycles prior to trying to conceive,
• 5 after dimethyl fumarate therapy which was stopped prior to conception,
• 3 after dimethyl fumarate therapy that was continued until confirmed pregnancy,
• 3 after glatiramer acetate therapy that was continued until confirmed pregnancy,
• 2 after teriflunomide therapy following washout, and
• 2 after natalizumab therapy that was stopped in advance of fertility treatment.

No other DMT scenarios were associated with more than 1 miscarriage.

These findings may be biased, as the participants were self-referred, so few pregnancies were likely unplanned.

The researchers concluded, “Our study provides real world data that there does not appear to be an increase in first-trimester miscarriages for women with MS. It is important to continue prospective MS pregnancy registries to collect this important information, especially as types of DMTs and use of DMTs continue to expand and impact quality of life for women of reproductive age living with MS.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.