Women with multiple sclerosis can be reassured that should they choose to become pregnant, they are generally not at any greater risk of adverse pregnancy or birth outcomes than are similar women without the disease, according to a retrospective cohort study.
The findings should have important clinical implications for this group of patients, because about three-quarters of people with MS are women and the clinical onset of the disease most often occurs in early adulthood, just when many are considering starting a family, Mia L. van der Kop and her coauthors wrote online June 27 in Annals of Neurology.
Studies have shown that one-fifth to one-third of women with MS bear children after disease onset.
Ms. van der Kop and her coinvestigators at the University of British Columbia, Vancouver, linked clinical data from the British Columbia (BC) MS clinics’ database with outcomes data from the BC Perinatal Database Registry (BCPDR) to examine whether maternal MS was associated with adverse neonatal and delivery outcomes and to determine what factors, if any, were associated with risk (Ann. Neurol. 2011 June 27 [doi: 10.1002/ana.22483]).
Since the BCPDR established full provincial coverage in 2000, it has captured more than 99% of births in BC and has gathered information on a wide range of outcomes and potentially confounding variables. The BC MS Clinics’ database is estimated to capture 80% of the MS population in BC.
The investigators measured disability via the Expanded Disability Status Scale (EDSS) score assigned closest to the time of delivery. MS mothers were classified as having a normal neurologic examination score (EDSS = 0), mild disability (EDSS = 1-3), or moderate to severe disability (EDSS at least 3.5).
With the use of a unique personal health number, all female patients who were registered at one of the four MS clinics in BC from 1980 through 2008 were linked at an individual level to births occurring in BC between April 1998 and March 2009. Patients’ names and dates of birth were used to confirm the accuracy of linkage.
Of 7,056 female patients in the BCMS database, the investigators found matches in the BCPDR for 550 women (762 births). These births were compared with 3,048 births from a random sample of women in the general population who were frequency-matched for age, local health authority, and delivery year.
Births were included in the MS group if the mother had laboratory-supported or clinically definite MS (Poser or McDonald criteria) diagnosed by an MS specialist neurologist. Births to mothers whose disease onset occurred after delivery were excluded. Births to individuals with an ICD-9 or -10 code for MS in the BCPDR were excluded from the comparison group. After exclusions, the data set contained 432 births to 321 women with MS and 2,975 births to 2,958 women without MS.
A greater proportion of births in the MS group were to women who were nulliparous, primigravid, hypertensive, or had smoked during pregnancy. A greater proportion of births in the comparison group were to mothers with diabetes during pregnancy and a history of multiple therapeutic abortions. All other baseline characteristics were similar.
Maternal MS was not associated with assisted vaginal delivery (odds ratio, 0.78) or cesarean section (OR, 0.94). The proportion of elective cesarean sections was similar in both the MS and comparison groups (18.6% vs. 16.1%, respectively), and the indication for cesarean delivery did not differ between groups. Delivery outcomes were not associated with either an older age at MS onset or longer disease duration.
The degree of disability in MS mothers was not significantly associated with higher odds of a cesarean section or an assisted vaginal delivery, compared with women who had a normal neurologic examination.
A very small difference in mean birth weight between babies in the two groups was neither clinically nor statistically significant. Gestational age did not differ according to MS clinical factors.
Data on maternal body mass index were missing for 31% of births, so a regression model was developed that excluded BMI. In this model, diabetic status during pregnancy had an interactive effect among participants with diabetes during pregnancy. The mean birth weight of babies born to mothers with MS was 232 g greater than that of babies in the comparison group. Diabetes was not a significant factor, once BMI was taken into account. Regardless of BMI, there were no significant differences in birth weight according to MS clinical factors.
"However, MS mothers were more often overweight or obese. Because high BMI is associated with adverse pregnancy and birth outcomes, women with MS [should be encouraged] to optimize their weight when planning a pregnancy. This also highlights the importance of considering BMI in future investigations of pregnancy-related outcomes," the researchers wrote.