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Pregnancy and childbirth, Women's health

Managing MS during pregnancy

Opinion on how MS impacts pregnancy is based largely on data that predate the current era of active treatment and the newer generation of disease-modifying therapies (DMTs). In this section I have therefore addressed many of the important issues that women who are considering pregnancy need to understand, including:

  • the effect of pregnancy on the course of MS
  • how to manage relapse during pregnancy
  • the role of naturally occurring interferon-beta and its possible implications for women with MS taking therapeutic interferon-beta
  • management of MS symptoms and morning sickness during pregnancy
  • the crucial issue of DMT safety and possible teratogenic effects on the developing foetus.

Will pregnancy affect the course of my MS?

Yes, pregnancy effects on MS have been observed at a group level, though it is difficult to notice changes in individuals. It is well known that MS attack rates drop during the second and third trimesters of pregnancy and relapses rebound again in the first 6 months after delivery. However, only a minority of women with MS have post-partum relapses. Breastfeeding may blunt the post-partum rebound, but this is not absolute. Therefore, most neurologists now recommend starting or restarting DMTs soon after delivery to try and prevent post-partum relapses.

At a population level, the more children you have, the better your overall prognosis. This effect is small and is based on studies done in the pre-DMT era. It may be due to the immunological effects of pregnancy that work like a DMT in MS. Immunologists have tried to understand this phenomenon in the hope of developing treatments for MS that mimic the pregnancy state.

How is a relapse managed during pregnancy?

In the event of having a relapse during pregnancy, a short course of high-dose corticosteroids can be considered. However, I limit using steroids to disabling and/or severe relapses, especially early in the first trimester, as there is a small risk of orofacial abnormalities (cleft lip and palate) and reduced birth weight from exposure of the developing foetus to high-dose steroids. There is also a risk of precipitating gestational diabetes in women receiving high doses of steroids during pregnancy. In the rare situation of a severe relapse unresponsive to high-dose steroids, plasma exchange may need to be considered.

Could neutralising antibodies to therapeutic interferon-beta affect my baby?

Naturally occurring interferon-beta is a cytokine (cell-signalling agent) produced by the body to help fight infections. As there is only one human interferon-beta, antibodies to therapeutic interferon-beta (IFN-beta) will neutralise the body’s own natural interferon-beta. If you are taking IFN-beta for your MS, there is thus a theoretical risk that neutralising antibodies (NABs) to the DMT might cross the placenta and affect the role of human interferon-beta in foetal development.

Interferon-beta is important for innate immunity and neutralising your own interferon-beta may put you at risk of getting viral infections. Interferon-beta also plays a role in foetal bone development, but the placenta does not mature in relation to immunoglobulin transfer until near the end of the second trimester of pregnancy, so it is unlikely that sufficient NABs cross the blood ̶ placental barrier to affect foetal bone development. However, in the third trimester, NABs will cross over the placenta into the foetal circulation and may impact the baby’s innate immunity. Despite these theoretical concerns, there is no indication from published data to support these potential adverse effects of NABs on IFN-beta.

If I fall pregnant while on a DMT, will this affect the baby?

This depends on which DMT you are taking and what you mean by ‘affecting the baby’. We worry most about teratogenic effects, which describe congenital malformations. Teriflunomide, S1P modulators and cladribine are generally classified as drugs that may be teratogenic, and hence precautions need to be taken so as not to fall pregnant on these agents. Foetal malformations usually occur very early in foetal development, often before the woman knows she is pregnant; therefore, it is difficult to do anything about it once foetal exposure occurs. Despite this, even for women who are on these agents and fall pregnant, we don’t automatically recommend termination of pregnancy. We refer them to the high-risk pregnancy clinic to discuss the options with an obstetrician. Many women continue their pregnancies with an uneventful outcome and a normal baby. On the other hand, some women choose the option of terminating their pregnancy.

A large amount of data from MS pregnancy registries and post-marketing surveillance indicates no increased risk of major congenital anomalies or spontaneous abortions (miscarriages) after exposure to interferon-beta or glatiramer acetate. Most neurologists are, therefore, comfortable with their female patients falling pregnant on these agents, continuing the treatment through pregnancy and then breastfeeding their babies.

Fumarates (dimethyl fumarate [Tecfidera], diroximel fumarate [Vumerity]) are not teratogenic and are unlikely to have a negative impact on pregnancy outcomes. We need more data from registries and post-marketing surveillance before we can be confident that the fumarates are safe during pregnancy. However, these agents are prodrugs and converted to monomethyl fumarate, which is part of our metabolism, so it is very unlikely that the fumarates will cause problems. I don’t have an issue with women falling pregnant on the fumarates and continuing them through pregnancy, but there is conflicting advice about this.

Should I continue taking drugs for my MS symptoms during pregnancy?

Yes and no. It depends on what the medications are for and whether they are safe during pregnancy. Ideally, you should wean off any symptomatic therapies or at least change to alternative medications that are safe to take during pregnancy. It is important to try and plan your pregnancy and if necessary be referred to a special medical pregnancy clinic so that these issues can be addressed. Many women with MS find that their MS-related symptoms improve during pregnancy, and they can do without symptomatic therapies. However, unless you are prepared to wean yourself off symptomatic therapies you won’t know.

Physical therapies should be continued during pregnancy. One could argue that everyone with MS should be physically active and do pelvic floor exercises. Pregnancy and childbirth may impact bladder and bowel function, so it is important to see a pelvic floor therapist to start pelvic floor exercises. The latter are taught to women in antenatal classes.

How do you treat morning sickness or hyperemesis gravidarum during pregnancy?

Treating morning sickness or hyperemesis gravidarum is no different in women with MS than in the general population. It involves hydration, vitamin supplements (in particular, thiamine) and the judicious use of antiemetics (for example, cyclizine, prochlorperazine, promethazine, chlorpromazine, metoclopramide and domperidone). If the vomiting extends into the second trimester, ondansetron can be used. In very severe cases of morning sickness, steroids may be required; for example, hydrocortisone 100 mg twice daily can be converted to prednisolone 40 ̶ 50 mg daily by mouth, which can then be tapered to the lowest level that still controls symptoms. For patients taking a fumarate, try and take your medication later in the morning when you are less likely to vomit.

What dose of vitamin D do you advise during pregnancy?

During pregnancy vitamin D requirements are increased and I recommend doubling the dose for supplementation from 4,000 IU of vitamin D3 to 8,000 IU per day. At the same time, women who are pregnant should be on iron and folate supplements that should ideally be started before falling pregnant.

References

Krysko KM et al. Treatment of women with multiple sclerosis planning pregnancy. Curr Treat Options Neurol 2021;23:11.

Other articles in this series on Pregnancy and childbirth
Planning for pregnancy
Preparing to give birth
Breastfeeding if you are on a DMT
Concerns about parenting

Stages of MS

What type of MS do I have?

MS has historically been classified into different subtypes, and this subdivision dictates what treatments you are eligible for. These MS disease subtypes are not supported biologically, however, and many MS neurologists are of the opinion that MS is one disease.1

Key points

  • The difference between relapsing MS and non-relapsing progressive MS is explained.
  • The stages of MS have different labels, for historical development and reimbursement reasons, but biologically MS is one disease.
  • From a treatment perspective, the key thing is to know if your MS is active or inactive.
  • Active MS can be differentiated by relapses, MRI evidence of disease activity and raised neurofilament levels in the cerebrospinal fluid.

Type of MS

You should be able to classify yourself as having either relapsing MS or non-relapsing progressive MS. Knowing what type of MS has been diagnosed and whether your MS is active or inactive will allow you to ask your MS neurologist questions about the MS treatments available to you. 

Around 85–90% of people with MS start with so-called relapse-onset MS, i.e. they have a definite attack that is usually followed by a period of complete or incomplete recovery. A single attack may be labelled as a clinically isolated syndrome (CIS): it does not fulfil the current diagnostic criteria for full-blown MS, but it means someone is at risk of further attacks and hence of developing MS in the future.

EDSS, Expanded Disability Status Scale

Once you have more attacks, either clinically in the form of relapse or subclinically with new lesions on magnetic resonance imaging (MRI), then you are usually diagnosed as having MS. The diagram below illustrates the typical course of repeated relapses and remissions, with worsening disability over time, that characterises so-called relapsing–remitting MS (RRMS).

After a variable period, people with relapse-onset MS may notice worsening neurological function without improvement. This is called secondary progressive MS (SPMS) and it can occur with superimposed relapses (so-called relapsing SPMS [RSPMS]) or without relapses.

EDSS, Expanded Disability Status Scale

A small number of people with MS (10–15%) will present with worsening neurological function without a prior history of relapses; this is called primary progressive MS (PPMS).

Interestingly, some people with PPMS go on to have relapses, and this is referred to as progressive relapsing MS (PRMS).

EDSS, Expanded Disability Status Scale

Rarely, someone may present with worsening neurological function, similar to PPMS, but have a prior history of just one relapse. This is referred to as single-attack progressive MS (SAP), but most MS specialists classify these patients as having SPMS. 

In summary …

  • Relapsing MS captures all people with MS who are still having relapses, i.e. within the last 2 years, and includes RRMS, RSPMS and PRMS.
  • Non-relapsing progressive MS refers to SPMS and PPMS: these latter two groups should have no history of recent relapses, i.e. in the last 2 years.

To further confuse things, non-relapsing progressive MS used to be referred to as chronic progressive MS (see below). 

Why is this important?

Different DMTs are licensed for different types of MS, and many treatment guidelines specifically state the type of MS for which a particular drug can be used.

Is MS one or more diseases?

In the past, MS was one disease: either you had MS, or you did not. The stages were referred to as early relapsing MS or chronic progressive MS, but MS was still one disease. 

When disease-modifying therapies (DMTs) were developed, MS was split into multiple sub-types. This categorisation was driven by commercial considerations, and it allowed interferon-beta to be licensed in the US under the Orphan Drug Act. The classification of orphan disease in the US requires there to be fewer than 200,000 people with that diagnosis. Dividing MS into RRMS, SPMS, PPMS and later CIS ensured that each category met this criterion. 

Since then, PRMS and radiologically isolated syndrome (RIS) have been added as potential subtypes. These classifications tend to be arbitrary and overlap, but there is no biological basis to support MS being more than one disease. 

Is your MS active or inactive?

From a treatment perspective, it is important to know if your disease is active or inactive. In active MS, there is evidence of ongoing inflammation in the brain and spinal cord. If you are having relapses, are developing new lesions on MRI or have raised neurofilament (NFL) levels in your cerebrospinal fluid (CSF) or blood, your MS is active. 

Active MS responds to anti-inflammatory treatments; inactive MS is less responsive to currently licensed DMTs. 

Criteria for ‘active’ MS accepted by many MS health professionals. CSF, cerebrospinal fluid; NFL, neurofilament light.
*Some neurologists accept 24 months, 36 months or even longer when assessing MRI activity. There is no international consensus on the gap between the baseline and new MRI scan to define active disease.


The term progressive MS refers to the stage of MS when your disability gets worse – independent of relapses, and possibly of focal inflammatory lesions. I say ‘possibly’, because our current MRI scans don’t show new or enlarging microscopic lesions but only those that are larger than ~3–4 mm. NFL measurements in either the CSF or blood have the advantage of being additive and integrating inflammatory activity. In my experience, about one in ten patients classified as ‘inactive’ based on clinical and MRI activity is found to have active MS when CSF NFL levels are analysed. Unfortunately, however, many MS neurologists, regulators and payers do not accept this latest definition of MS disease activity because tests for NFL levels are currently not widely available. 

In conclusion, knowing the type of MS you have and whether your disease is active or inactive will allow you to discuss with your MS specialist the kinds of treatment available to you. 

References

Giovannoni G, et al. Smouldering multiple sclerosis: the ‘real MS’. Ther Adv Neurol Disord 2022;15:17562864211066751.