In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This sheet talks about whether exposure to ankylosing spondylitis may increase the risk for birth defects over that background risk. This information should not take the place of medical care and advice from your health care provider.

What is ankylosing spondylitis?

Ankylosing spondylitis (AS) is a kind of arthritis that mostly affects the spine. Arthritis is a general term for inflammation or swelling of the joints in the body. Symptoms of AS can include swelling, stiffness and pain. Sometimes, advanced AS can lead to new bone formation that causes the spine to become stuck in one position or become fused. Signs of AS usually start in young adults.

Will having ankylosing spondylitis make it harder for me to get pregnant?

Women with AS probably have a similar chance of getting pregnant (fertility rate) as compared to women without this condition.

How will pregnancy affect my symptoms?

Health care providers are not able to predict how a woman’s symptoms might change, if at all, during a pregnancy. However, some studies suggest that most women’s symptoms stay about the same during pregnancy. Some women report an increase in certain symptoms, especially as the pregnancy gets further along. Other women’s symptoms actually improve during pregnancy, but pregnancy does not appear to protect against AS flare-ups like it may for other autoimmune conditions. A flare-up of symptoms is common in the first few months after delivery, but this does not mean that the severity of the symptoms will be long-term.

Does having ankylosing spondylitis increase my chance for miscarriage?

There are no published studies looking at AS and miscarriage. At this time it is unknown. Additional studies are needed.

Can having ankylosing spondylitis increase my chance for my baby to have a birth defect?

There have not been any published studies to date looking at AS by itself to check for birth defects. Many people with AS use medication, so the results from any studies might be due to the medication instead of to the AS itself. We recommend discussing your treatment options with your health care provider. Your healthcare provider can work with you to manage your medical condition during pregnancy.

Does having ankylosing spondylitis mean I have a higher chance for a pregnancy complication?

Several studies have not found an increased chance for pregnancy complications in women with AS. One study suggested that AS did increase the chance for delivery before 37 weeks (prematurity), low birth weight and/or the need for cesarean delivery. The risk for pregnancy complications may be linked with the severity of AS and/or whether a woman has additional medical conditions or develops preeclampsia (very high blood pressure during pregnancy). It is possible for a woman with AS to have a vaginal delivery.

I am taking medication for ankylosing spondylitis. Can I take my medication during pregnancy?

Some medicines used to treat AS are known to cause birth defects, but others have not been associated with a risk to the developing baby. For information on specific therapies see our medication fact sheets at or contact MotherToBaby toll-free at 1-866-626-6847. It is important that you discuss treatment options with your health care providers when planning pregnancy, or as soon as you learn that you are pregnant.

Can I breastfeed if I have AS?

AS does not appear to affect a woman’s ability to breastfeed.

Can I take my medicines for ankylosing spondylitis while breastfeeding?

Many medications for ankylosing spondylitis can be used while breastfeeding. However, while some medications are low risk, others may be more concerning. For information on specific medications see our fact sheets or contact MotherToBaby. Be sure to talk to your health care provider about all your questions on breastfeeding.

What if the father of the baby has ankylosing spondylitis?

Certain medicines used to treat ankylosing spondylitis could have an effect on a man’s sperm production. This could make it harder to get pregnant. Other medicines are not thought to have an effect on sperm. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures and Pregnancy at

MotherToBaby is currently conducting a study looking at ankylosing spondylitis and the medications used to treat AS in pregnancy. If you are interested in taking part in this study, please call 1-877-311-8972 or sign up at


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