- It is well established that the rate of multiple sclerosis (MS) relapses decreases during pregnancy.
- Although some studies have also linked fewer relapses to breastfeeding, they have suffered from methodological shortcomings.
- Authors of a large trial in Germany, which guarded against these common problems, recently reported a significant relapse reduction for the first six months after giving birth among women with MS who breastfeed exclusively for at least two months.
As an immunological disease that is usually diagnosed before the age of 40 in about three times as many women as men, multiple sclerosis (MS) affects many individuals who hope to carry a child to term and nurture it thereafter. In the 1950s, experts assumed that pregnancy would be nothing but harmful to these women. Many studies since then have demonstrated that the risk of an MS relapse actually plummets during pregnancy, especially in the third trimester, only to increase again after birth. Recently, a large study in Germany also found that exclusive breastfeeding for at least two months diminishes the odds of relapse for six months after the baby is born . Understanding the immunological changes taking place that mediate these shifting risks may eventually lead to novel treatments.
The symptoms of MS—which vary greatly among patients—result from the immune system mistakenly identifying as foreign the insulating coating that protects nerves, and enables these cells to transmit signals as quickly as they do. The signals, therefore, become disrupted, potentially affecting any part of biology and behavior from speech to bladder control. About 85% of people with MS experience the disease as a series of relapses, whereby their symptoms appear sporadically, lasting for maybe a few weeks during each relapse before fading away again.
The most widely cited study of MS relapses and pregnancy was conducted in the 1990s . It followed 269 pregnancies, from the year before pregnancy to a year after birth, among European women residing in 12 different countries. This set-up allowed the researchers to compare the participants’ relapse rates during different periods of pregnancy with their individual baselines—established during the 12 months before they became pregnant. It uncovered a 70% reduction in disease activity during the third trimester .
Findings on the rate of MS relapses during breastfeeding, however, have been less readily accepted. This is because research in the area has tended to struggle with two issues that could muddy the results. The first problem is one of self-selection: women who feel well enough to breastfeed are reasonably likely to be those less frequently troubled by relapses anyway, so a finding that breastfeeding is associated with lower rates of relapses might be an artifact of these women’s disease being less severe. The second problem has been that most studies have not distinguished women who exclusively breastfeed from women who breastfeed while supplementing their infants’ diet with other foods. This distinction matters a great deal for the immunological changes that take place in a woman’s body.
The recent study in Germany overcame both of these problems. Researchers can’t—and shouldn’t—tell women whether to breastfeed or not, but they can monitor and compare the symptoms of those who decide either way. (Indeed there was no relationship between pre-pregnancy disease severity and whether or not women in this study breastfed.) The study also evaluated women who breastfed exclusively for a minimum of two months separately from non-exclusive breast feeders. In all, it followed 201 women over four-and-a-half years from before they become pregnant, interviewing them regularly about their symptoms, the drugs they were taking, their pregnancies and breastfeeding habits.
Out of these 201 women, 120 intended to feed their infant their own milk without supplementation for two months or more. Among this group, 24% experienced a relapse in the six months after their child was born. That proportion is significantly lower than the 38% of women who relapsed among those who either did not breastfeed at all or breastfed with supplementation. The authors considered these effects large enough to conclude that “exclusive breastfeeding acts like a MS treatment with a natural end date.”
But what explains the differences? The reason that distinguishing exclusive and non-exclusive breast feeders is thought to be so important is that introducing regular formula or solid food into an infant’s diet prompts hormonal changes in a woman’s body that prepare it to restart ovulation. Getting one’s period back after having a baby is associated with a rise in a pro-inflammatory signaling molecule called tumor necrosis factor-alpha (TNF-alpha). Although the details of the mechanisms involved are not entirely clear, and other immune factors are likely involved, at least one other study has linked lactational amenorrhea (not having periods while breastfeeding) with a decrease in the CD4 cells that produce TNF-alpha . The suppression of CD4 cells that occurs during pregnancy—as part of a suite of changes that prevent a women’s body rejecting a fetus—is also thought to explain the quelling of MS-relapse risk at that time.
As the authors of a review on the topic have noted, plenty more research needs to be done to tease out the immunological details of these shifting risks, including more completely identifying the pro-inflammatory molecules involved . That will be necessary before this line of inquiry can lead to new drug targets, which is certainly possible in the future. Until then, the message from the German study is clear: exclusive breastfeeding is not only best for the infant but also for a new mother with MS. And that’s especially good news for women who struggle with a condition for which the best medications are already extremely costly, and seem to be getting ever more so each year . Although breastfeeding isn’t free—it costs time and energy—it should improve the symptoms for those who choose and are able to do it, without straining their bank accounts.
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Professional science writer & editor