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.


Aldurazyme should only be used during pregnancy if medically necessary, as determined by your doctor. Safety data describing the use of Aldurazyme during pregnancy consists of only 2 case reports. Allergic reactions can occur when the medication is infused intravenously. These reactions could cause oxygen deprivation, brain damage, or death in the baby. Medication is often given before the infusion to prevent these reactions.

What is Aldurazyme?

Aldurazyme is a medication that treats a rare genetic disease called mucopolysaccharidosis type I (MPS I). Aldurazyme contains the active ingredient laronidase. It is given as a weekly 3 to 4-hour intravenous infusion by a healthcare practitioner. This medication is only available by a prescription from your doctor.

What is Aldurazyme used to treat?

Aldurazyme is used to treat certain types of MPS I and can help relieve some of the complications, including heart, bone, and breathing problems, associated with MPS I. MPS I is a potentially life-threatening condition caused by a deficiency of a specific protein (alpha-L-iduronidase) that helps your body digest large carbohydrates. These carbohydrates accumulate in people with MPS I and damage the body’s organs. The symptoms of this disease usually develop in childhood and can differ depending on whether the child has severe or attenuated (milder) disease. Although children with severe disease generally do not live into adulthood, those with attenuated disease can maintain relatively normal lives into adulthood. 

The following are some of the symptoms that can occur in people with MPS I:

  • Enlarged head
  • Fluid in the brain
  • Enlarged tongue, liver, and/or spleen
  • Narrowed airways, leading to breathing difficulties and infections
  • Clouding of the cornea, leading to vision loss
  • Ear infections and hearing loss
  • Short stature
  • Spinal stenosis (narrowing of the spinal cord)
  • Heart disease
  • Joint deformities
  • Carpal tunnel syndrome
  • Mental retardation (in the severe form of MPS I)

How does Aldurazyme work?

Aldurazyme provides your body with a protein that is similar to the deficient protein in people with MPS I (alpha-L-iduronidase). This helps your body digest the carbohydrates that accumulate in MPS I and alleviates some of the symptoms of MPS I, such as difficulty breathing, joint disease, and heart problems. Aldurazyme is unlikely to improve intellectual or mental deficiencies associated with MPS I because the medication is not expected to enter the brain. Although Aldurazyme can help improve the symptoms of MPS I, it is not a cure for the disease.

If I am taking Aldurazyme, can it harm my baby?

Aldurazyme should only be used during pregnancy if clearly needed, as determined by your doctor. There are no adequate or well-controlled studies on the use of Aldurazyme in expecting moms, and it is unknown if Aldurazyme crosses the human placenta to reach the baby. A study in pregnant animals found no evidence that Aldurazyme harmed the offspring. However, human studies are needed to confirm the safety of Aldurazyme use in pregnancy because findings in animal studies are not always consistent with human response.

Some experts consider the benefits of treatment with Aldurazyme to outweigh potential risks to the baby. A study showed that temporarily discontinuing Aldurazyme due to pregnancy led to a decline in the mom’s condition. Pregnancy can worsen many of the complications associated with MPS I, and similarly, MPS I can lead to pregnancy complications. Your doctor will determine if Aldurazyme is medically necessary, or if it should be discontinued until after the birth of your baby.

The data for the use of Aldurazyme during pregnancy only consists of two case reports. An expecting mom with MPS 1 became pregnant while receiving laronidase once weekly. She received laronidase for a duration of less than 4 weeks during pregnancy. The medication was then discontinued. She delivered her baby prematurely, but the baby was healthy at birth. The cause of the premature birth was unknown, but it was thought to be due to MPS I.

Another case report describes a woman who had received laronidase for 3 years and continued her treatment through pregnancy. She delivered a healthy baby with no problems related to the use of laronidase. A follow-up visit 2.5 years after the baby’s birth confirmed that the child was growing and developing normally.

Intravenous infusions of Aldurazyme can lead to low blood pressure and allergic reactions, including a life-threatening reaction, called anaphylaxis. Anaphylaxis can lead to death in the mom. These reactions also reduce blood flow to the placenta and deprive the baby of oxygen, leading to brain damage or death. Your healthcare practitioner will likely provide medications prior to your infusion to prevent allergic reactions from occurring.

Bottom line: Aldurazyme should only be used during pregnancy if clearly needed, as determined by your doctor. There have been no studies that have looked at the safety of Aldurazyme during pregnancy. Intravenous infusions of Aldurazyme can lead to reactions that could harm your baby. Medication is usually given before the infusion to prevent these reactions.

If I am taking Aldurazyme and become pregnant, what should I do?

If you have been receiving intravenous infusions of Aldurazyme and become pregnant, you should contact your doctor immediately. Your doctor will decide if Aldurazyme is medically necessary, or if your medication should be temporarily discontinued.

If I am taking Aldurazyme, can I safely breastfeed my baby?

Caution should be used if intravenous infusions of Aldurazyme are given to a breastfeeding mom, according to recommendations from the FDA. It is unknown if Aldurazyme passes into human breast milk. No studies have looked at the safety of taking Aldurazyme while nursing, and the data that is available only consists of one case report.  A breastfeeding mom received intravenous infusions of Aldurazyme. The medication could not be detected in her breast milk, and no side effects from the medication were reported in her breastfed baby. Follow-up reports indicated that her baby’s growth was normal at up to 1 year of age and development was normal at 2.5 years of age. If your doctor determines that Aldurazyme is medically necessary while nursing, breast milk can be pumped and discarded for 8 to 12 hours after the infusion has been completed to reduce your baby’s exposure to the medication. During this time, moms can give their baby breast milk that has been pumped prior to the infusion. Breastfed babies whose moms received Aldurazyme should be monitored for side effects, such as skin rash, swelling, low blood pressure, and respiratory infections.

Bottom line: Caution should be used if Aldurazyme is given while breastfeeding. It is unknown if this medication passes into breast milk, and the effects of this medication in the breastfed baby have not been studied.

If I am taking Aldurazyme, will it be more difficult to get pregnant?

No studies have looked at the effects of Aldurazyme on fertility. However, MPS I may cause fertility problems. The undigested carbohydrates in people with MPS I have been shown to collect in the ovaries, placenta, and brain. Animal studies have shown that female mice with MPS I had poor fertility. Male mice with MPS I had reduced sperm counts and changes in the characteristics of sperm. No studies have been conducted in humans looking at the effects of MPS I on fertility.

If I am taking Aldurazyme, what should I know?

Aldurazyme should only be used during pregnancy if clearly needed, as determined by your doctor. No studies have looked at the safety of Aldurazyme in expecting moms. Intravenous infusions with Aldurazyme can cause allergic reactions that could harm your baby. Healthcare practitioners will likely provide medic
ation prior to the infusion to prevent these reactions.

Caution should be used if Aldurazyme is taken while breastfeeding. It is unknown if this medication passes into breast milk, and the medication’s effects on the breastfed baby are unknown.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of Aldurazyme during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry's expert reports about digestive system disorders and the individual medications used to treat them here.  Additional information can also be found in the links below. 

For more information about Aldurazyme during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or check the following links:

National Organization for Rare Disorders: Mucopolysaccharidosis Type I

WebMD: Mucopolysaccharidosis I (MPS I)

U.S. National Library of Medicine: LACTMED: LARONIDASE

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Last Updated: 24-03-2019
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.