Breastfeeding does not appear to protect moms with MS against relapse of their disease, new research finds.

Though pregnancy itself is associated with fewer relapses among women with MS (a chronic autoimmune condition in which immune-system cells attack the myelin sheaths that protect nerves in the central nervous system), breastfeeding’s effect on relapse (a period during which MS symptoms reappear or worsen) has been hard to pin down. Risk of relapse rises substantially in the first few months after childbirth. (As I reported in late June, MS does not appear to increase risk of complications during pregnancy and childbirth.)

The current study, published online Wednesday in the journal Neurology, looked at data from 2002 to 2008 regarding breastfeeding duration and MS relapse related to 302 births to 298 women from 21 MS treatment centers in Italy.

All told, 104 women breastfed for at least two months; the others did so for less than two months or not at all. During the first year after delivery, 112 women had one relapse and 20 women had two or more relapses. Relapses apparently led 39 of the women to cease breastfeeding.

After data were adjusted for all manner of potentially confounding factors (age at onset of disease and at pregnancy, disease duration, disability level, relapses in the year prior to pregnancy and during pregnancy, treatment with disease-modifying drugs, and exposure to toxins), the only clear predictors of postpartum relapse were occurrence of relapses during the year before pregnancy and during pregnancy.

The research may inform the choices women with MS make (with their neurologists) about when to resume treatment with disease-modifying drugs (which are typically discontinued during pregnancy) after giving birth. Women should now be counseled that breastfeeding won’t protect against relapse, the study concludes.

Further, because existing drug treatments for MS haven’t been shown to be safe to use while breastfeeding, women have to choose between breastfeeding and taking those drugs. The latter might be the better option for many women, especially those whose disease activity or risk of relapse is high.