NEW YORK (Reuters Health) – After pregnancy, women with multiple sclerosis may substantially reduce their risk of relapses if they breastfeed their infants, without adding supplemental formula feedings, for at least 2 months after birth.

That’s the conclusion of researchers in California, who also found that women who reinitiated MS medications within 2 months after birth actually had a higher rate of relapse than other women, regardless of whether they breastfed or not.

The research team at Stanford University in Palo Alto and at Northern California Kaiser Permanente Division of Research, Oakland, will report their findings on April 28 at the American Academy of Neurology’s 61st annual meeting in Seattle.

“Women with MS have fewer relapses during pregnancy and an unusually high risk of relapse in the first 3-4 months postpartum,” Dr. Annette Langer-Gould, who will be presenting the research, told Reuters Health.

“Whether breastfeeding is beneficial or harmful in MS is not certain,” she continued. “The few previous studies in women with MS have suggested that breastfeeding has no effect, but they did not distinguish between exclusive and non-exclusive breastfeeding. Current treatments used to reduce the risk of relapses in MS are not recommended for use during pregnancy or lactation and their effect on postpartum relapses have never been studied.”

“Thus, patients have to choose whether to forego nursing (and the health benefits to the infant) and resume treatment, or nurse and remain untreated, without clear evidence to support either practice.”

To shed light on these issues, Dr. Langer-Gould’s team prospectively followed 32 pregnant women with MS throughout their pregnancies and for the first postpartum year.

Forty-eight percent of the women breast fed exclusively for at least 2 months, while the remaining 52% did not breastfeed or else began regular supplemental feedings within 2 months.

The rate of postpartum relapse was 87% among those who did not breastfeed exclusively vs 36% of those who did. After adjusting for disease severity and age, the hazard ratio for relapse among those who did not exclusively breastfeed was 7.1 (p = 0.002).

Exclusive breastfeeding results in prolonged lactational amenorrhea and ovarian suppression, which may have antiinflammatory effects, Dr. Langer-Gould explained. After supplemental infant feedings are introduced, maternal ovarian activity and menses return.

“One might say that distinguishing between breastfeeding exclusively, some, or not at all is more biologically relevant than just breastfeeding, yes or no,” she said.

Dr. Langer-Gould said she was “definitely surprised” by the finding that women who resumed MS therapies within 2 months postpartum had a significantly higher risk of postpartum relapses (p < 0.001). “Our data suggest that it is most likely because they are not breastfeeding.” If findings from this small study are replicated in larger trials, she suggests that “physicians may want to consider extending maternity leave for at least 2 months for women with MS so they can breastfeed exclusively.”