OBJECTIVE

To determine if exclusive breastfeeding protects against postpartum relapses of multiple sclerosis (MS) and, if so, whether this protection is related to prolonged lactational amenorrhea.

DESIGN

We conducted structured interviews to assess clinical, menstrual, and breastfeeding history during each trimester and 2, 4, 6, 9, and 12 months postpartum and collected neurological examination findings from the treating physicians of women with MS. Hazards ratios (HRs) were adjusted for measures of disease severity and age.

SETTING

Kaiser Permanente Northern California and Stanford University.

PARTICIPANTS

We prospectively enrolled 32 pregnant women with MS and 29 age-matched, pregnant controls. Main Outcome Measure Postpartum relapse.

RESULTS

Of the 52% of women with MS who did not breastfeed or began regular supplemental feedings within 2 months postpartum, 87% had a postpartum relapse, compared with 36% of the women with MS who breastfed exclusively for at least 2 months postpartum (unadjusted HR, 5.0; 95% confidence interval, 1.7-14.2; P = .003; adjusted HR, 7.1; 95% confidence interval, 2.1-24.3; P = .002). Sixty percent reported that the primary reason for foregoing exclusive breastfeeding was to resume MS therapies. Women who breastfed exclusively had a later return of menses (P = .001) than women who did not, and lactational amenorrhea was associated with a reduced risk of postpartum relapses (P = .01).

CONCLUSIONS

Our findings suggest that exclusive breastfeeding and concomitant suppression of menses significantly reduce the risk of postpartum relapses in MS. Our findings call into question the benefit of foregoing breastfeeding to start MS therapies and should be confirmed in a larger study.