Ankylosing Spondylitis


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is ankylosing spondylitis?

Ankylosing spondylitis is a chronic (long-lasting) disease of the skeletal system. The condition is characterized by arthritis in the back and pelvis, specifically inflammation of the vertebrae of the spine and the connections between the lower spine and pelvis. Over time, this inflammation destroys and fuses together spinal vertebrae and the joint between the sacral spine and the iliac bones of the pelvis.

As the condition develops, the affected person experiences increasingly severe and progressive back pain, as well as stiffness of the spine, which may be worst in the morning and improve during and after exercise. The stiffening is related to vertebral bones fusing together and, over time, this deforms the spine, thereby interfering with posture and activities, such as walking. In combination with pregnancy, the back deformity, stiffness, and pain can worsen due to increasing mechanical stress from the growing womb, which normally often produces back pain, even in an uncomplicated pregnancy.

How common is ankylosing spondylitis during pregnancy?

The prevalence of ankylosing spondylitis in the human population ranges from 1 to 14 cases for every 1,000 people (0.1-1.4%) depending on the country and community. The condition is 2-3 times more common in men than in women and it typically affects young people. Initial symptoms begin prior to age 30 in 80 percent of cases, and prior to 45 years of age in more than 95 percent of cases. Thus, in women, the onset of the disease overlaps with their childbearing years and often with pregnancy. It is possible for the first symptoms of ankylosing spondylitis to appear during pregnancy when the body is under additional stress.

How is ankylosing spondylitis during pregnancy diagnosed?

Diagnosis of ankylosing spondylitis begins with a history and physical examination, performed in your doctors office. Your primary care physician (a family doctor or primary care internist) is the initial point of contact. Based on issues that, from your description, sound as if they are rooted in the muscular-skeletal system, he or she will ask you a series of questions in an attempt to narrow down the possible causes to a few conditions. The plausibility of each candidate condition will be considered in the context of the length of time over which the problems have developed, and in context of demographic factors, such as your age, country of origin, and ethnicity. Your medical history and history of family members also will be taken into account.

If the primary care physician suspects ankylosing spondylitis, or if she thinks that it could be one of several conditions involving inflammation, she may request laboratory tests, such as the erythrocyte sedimentation rate (ESR) or C-reactive protein. She also may order plain radiographs of your spine and, in some cases, a magnetic resonance imaging (MRI) scan of the pelvis. If you are pregnant and thus seeing an obstetrician on a regular basis, the obstetrician may take the role of the primary care physician, and order these tests. During the office visit, the physician will also perform a physical examination with emphasis on the musculoskeletal system. In particular, she will examine your posture, the natural curvature of your lower and upper back (lumbar lordosis and thoracic kyphosis), the range of motion of various joints, and flexibility.

In either case, unless the doctor is certain that you are suffering from simple mechanical pain (muscle or tendon pain connected with pregnancy and/or exercise), she will likely refer you to a rheumatologist. The rheumatologist will continue any workup that was started by the primary care physician. Often, even initial tests like the ESR are left for this specialist to order. Either way, there will be more laboratory tests and, if there has not been an MRI, it will probably be performed at this point.

In order to diagnose ankylosing spondylitis, your doctor, in the course of the laboratory and imaging workup, must rule out other conditions that look similar to ankylosing spondylitis. Such conditions include mechanical lower back pain, lumbar spinal stenosis (narrowing of the canal inside the spine that encloses and protects the spinal cord), and rheumatoid arthritis. One of the most important tests needed to distinguish ankylosing spondylitis from these other conditions is the presence of HLA-B27. A positive result is not associated with the other conditions.

Does ankylosing spondylitis cause problems during pregnancy?

Ankylosing spondylitis may flare up during pregnancy or appear for the first time during pregnancy. Additionally, it may exacerbate back and pelvic pain that are common towards the end of the pregnancy. Perhaps most significantly, limited range of motion in joints in and around the lower back and pelvis may make it difficult for you to deliver vaginally. In such cases, your baby will probably have to be delivered by cesarean section.

Does ankylosing spondylitis during pregnancy cause problems for the baby?

Ankylosing spondylitis in the mother does not affect her baby. However, medications form the basis of treatment of the condition. There are two main categories of drugs given for the condition, both of which carry the potential to harm the baby.

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the ankylosing spondylitis
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat ankylosing spondylitis during pregnancy?

Pregnant women with ankylosing spondylitis and their physicians face a clinical dilemma because drug treatment is the principal and most effective means of mitigating symptoms and flare-ups. There are two main categories of drugs that are effective. The first category is called “non-steroidal anti-inflammatory drugs (NSAIDs)“, which include drugs that you may know well, such as ibuprofen, and many others. There is some concern that NSAIDs given frequently in high doses early in pregnancy can cause spontaneous abortion (miscarriage) and possibly birth defects. Furthermore, and more definitely, NSAIDs given late in pregnancy (after 30 weeks gestation) can cause premature closure of the ductus arteriosus, a passageway that allows blood to flow from the pulmonary artery to the aorta during fetal life, thereby shunting oxygenated blood from the other direction to fetal tissues.

The other main category of drugs for ankylosing spondylitis is “tumor necrosis inhibitors.” These are not recommended, particularly near the end of pregnancy, because of concerns that they may interfere with the newborns immune system, although information from studies has been limited and the risk may be minimal.

Who should NOT stop taking medication for ankylosing spondylitis during pregnancy?

There is no specific group that should not stop taking medication for ankylosing spondylitis. However, this does not mean that everybody must stop taking medications. The decision to continue with your current drug regime, to taper down the dosage, or to replace one type of drug with another should be made in consultation with your doctors. Various non-drug and supportive treatments are available. These include exercise, physical
therapy, and guided stretching and may allow you to keep symptoms at a minimum with a reduced dosage of your usual medications.

What should I know about choosing a medication for my ankylosing spondylitis during pregnancy?

Given that NSAIDs and tumor necrosis inhibitors both have benefits, drawbacks, and risks, the decision on medications should be made together with your physician.

You may find Pregistrys expert reports about the individual medications to treat ankylosing spondylitis here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for my ankylosing spondylitis when I am breastfeeding?

There is some evidence that small amounts of certain tumor necrosis factor inhibitors may enter breastmilk, but this is based on limited studies and it is yet not possible to determine whether this presents any major risk. NSAIDs are considered fairly safe in mothers who are nursing. However, if you are concerned about unknown risks, simply do not breastfeed, as infants on baby formula probably do just as well as infants who are breastfed.

What alternative therapies besides medications can I use to treat my ankylosing spondylitis during pregnancy?

Exercise programs, physical therapy, and guided stretching may allow you to keep symptoms at a minimum with a reduced dosage of your usual medications. If your symptoms are mild, or you are in remission, such therapies may even allow you to eliminate your medications for the duration of pregnancy. Along with drug and non-drug therapies, cessation of smoking also can help alleviate ankylosing spondylitis for those women who do smoke, plus there are numerous other benefits of smoking avoidance both for you and the fetus.

What can I do for myself and my baby when I have ankylosing spondylitis during pregnancy?

You must balance realistically the risks of drug treatment versus the discomfort of no drug treatment. You need to be able to sleep and move around during your pregnancy. If you can manage with only minimal discomfort without medications, more power to you. Otherwise, work with your doctor on the choice of medication and the lowest dosage that will work for you. Initially, this could involve some trial and error with different dosing regimens.

Resources for ankylosis spondylitis in pregnancy:

For more information about ankylosing spondylitis during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or read the following articles:


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Last Updated: 11-02-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

Medications for Ankylosing Spondylitis