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The Risk of Methotrexate on Pregnancies

Pregnant woman decides to stop taking methotrexateMethotrexate is one of the more commonly used drugs for people living with rheumatoid arthritis (RA) and other rheumatic conditions. This medication was originally designed to treat cancer patients, so prescribed doses are low for RA patients. Unfortunately, methotrexate leads to a number of side effects that can be fairly serious.

Women who are prescribed methotrexate are explicitly warned not to attempt getting pregnant while taking the drug. This medication is a dihydrofolate reductase inhibitor that works to prohibit purine metabolism. Studies have shown that methotrexate will produce specific malformations in a developing fetus.

This RA drug can cause:

  • Abnormalities in the limbs and skull
  • Dysmorphic facial features
  • Developmental complications
  • Growth deficiencies
  • Mental retardation

The potential risk to a developing fetus means that patients of childbearing age need to be very careful while taking this drug.

Studies Look at the Risk for Pregnant Mothers

You should be aware of the risk for fetal anomalies and pregnancy loss that accompanies methotrexate. A rheumatoid arthritis clinical study conducted in France looked at female patients administered low doses of the drug during their first trimester. There were 28 participants and treatment was suspended before the 8 week gestation period in 26 of the participants.

Results showed several complications during the study:

  • 4 miscarriages
  • 5 terminated pregnancies
  • 3 babies born prematurely

(Quick Fact: This study occurred in 2004, and the researchers concluded that risks for complications could be mitigated if treatment was terminated as early into the pregnancy as possible.)

Further studies have since provided evidence suggesting that even taking a low (once per week) dose of methotrexate can be unsafe for pregnant mothers.

The experts agree that pregnancy should be avoided if either partner is currently taking methotrexate. In fact, patients are strongly advised to wait an additional amount of time after their treatment is discontinued before even attempting to get pregnant:

  • Men should wait at least 3 months
  • Women should wait for at least one ovulatory cycle

Although not clinically proven, there is a theoretical risk for sperm mutation in men who take methotrexate. However, the Journal of Rheumatology says that paternal methotrexate exposure at the time of conception has not historically produced complications with the fetus.

Don’t Take the Risk

Patients should play it safe and avoid any exposure to this form of medication when looking to get pregnant. The side effects are at best unpredictable which is probably not a risk most mothers want to take. Taking methotrexate during the first trimester will result in a roughly 10/42 chance of the fetus developing some abnormality.

In conclusion, women who are taking methotrexate are advised to stop their dosage at least 3 months before they attempt to conceive. They should also take some form of folic acid supplementation throughout their pregnancy. The American College of Rheumatology also recommends staying on a safe form of contraception for those 3 months after taking methotrexate.

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