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Azathioprine Pregnancy and Breastfeeding Warnings

Azathioprine is also known as: Azasan, Imuran

Medically reviewed by Last updated on Jan 27, 2021.

Azathioprine Pregnancy Warnings

Animal studies have revealed evidence of teratogenicity. There are no controlled data in human pregnancy. Congenital anomalies, including polydactyly, plagiocephaly, congenital heart disease, hypospadias, and bilateral talipes equinovarus have occurred. Leucopenia and/or thrombocytopenia have been reported in a proportion of neonates whose mothers took azathioprine throughout their pregnancies. There have been reports of premature birth and low birth weight (especially in combination with corticosteroids), and spontaneous abortion after either maternal or paternal exposure; some data suggest an increased risk of intrauterine growth retardation and prematurity. Chromosomal aberrations have also been reported.

Azathioprine has been reported to cause temporary depression of spermatogenesis in mice.

Benefit versus risk must be weighed carefully before using azathioprine in patients of reproductive potential. The patient should be apprised of the potential hazard to the fetus if azathioprine is used during pregnancy or if the patient becomes pregnant while taking this drug. Extra hematologic monitoring should be considered during pregnancy.

A National Transplantation Pregnancy Registry (NTPR) has been established to monitor maternal-fetal outcomes of pregnant women exposed to immunosuppressant drugs, including azathioprine. Physicians are encouraged to register patients by calling 1-215-955-4820 (USA).

AU TGA pregnancy category D: Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects. Accompanying texts should be consulted for further details.

US FDA pregnancy category D: There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Use is considered contraindicated unless the benefits outweigh the risks.

Rheumatoid arthritis: Contraindicated (US)

AU TGA pregnancy category: D
US FDA pregnancy category: D

Comments: Adequate methods of contraception should be encouraged in both male and female patients of reproductive age during, and for at least 3 months after treatment cessation.

See references

Azathioprine Breastfeeding Warnings

UK: Use is contraindicated.
AU and US: Caution is recommended.

Excreted into human milk: Yes

Drugs and lactation database (LactMed): Breastfeeding is considered acceptable.

Studies in women taking azathioprine at doses up to 200 mg per day for immunosuppression in inflammatory bowel disease, systemic lupus erythematosus, or transplantation have found either low or undetectable levels of its active metabolites in milk and infant serum. Cases of mild, asymptomatic neutropenia have been reported; however, long-term data for carcinogenesis are not available. Women with decreased activity of the enzyme that detoxifies azathioprine metabolites may pass on higher levels of drug to their infants via breast milk.

If the decision is made to use azathioprine during breastfeeding, it may be advisable to monitor the complete blood count with differential, and liver function tests in exclusively breastfed infants. Avoiding breastfeeding for 4 to 6 hours after a dose should significantly reduce the dose received by the infant in breast milk.

See references

References for pregnancy information

  1. Ostensen M "Optimisation of antirheumatic drug treatment in pregnancy." Clin Pharmacokinet 27 (1994): 486-503
  2. De Witte, DB, Buick MK, Cyran SE, Maisels MJ "Neonatal pancytopenia and severe combined immunodeficiency associated with antenatal administration of azathioprine and prednisone." J Pediatr 105 (1984): 625-8
  3. Saarikoski S, Seppala M "Immunosuppression during pregnancy: transmission of azathioprine and its metabolites from the mother to the fetus." Am J Obstet Gynecol 115 (1973): 1100-6
  4. Cerner Multum, Inc. "Australian Product Information." O 0
  5. Kirk EP "Organ transplantation and pregnancy: a case report and review." Am J Obstet Gynecol 164 (1991): 1629-34
  6. Cararach V, Carmona F, Monleon FJ, Andreu J "Pregnancy after renal transplantaiton: 25 years experience in Spain." Br J Obstet Gynaecol 100 (1993): 122-5
  7. Ramsey-Goldman R, Mientus JM, Kutzer JE, Mulvihill JJ, Medsger TA, Jr "Pregnancy outcome in women with systemic lupus erythematosus treated with immunosuppressive drugs." J Rheumatol 20 (1993): 1152-7
  8. Williamson RA, Karp LE "Azathioprine teratogenicity: review of the literature and case report." Obstet Gynecol 58 (1981): 247-50
  9. "Product Information. Imuran (azathioprine)." Glaxo Wellcome, Research Triangle Park, NC.
  10. Wing AJ, Brunner FP, Brynger H, et al. "Successful pregnancies in women treated by dialysis and kidney transplantation." Br J Obstet Gynaecol 87 (1980): 839-45
  11. Pirson Y, Van Lierde M, Ghysen J, Squifflet JP, Alexandre GP, van Ypersele de Strihou C "Retardation of fetal growth in patients receiving immunosuppressive therapy." N Engl J Med 313 (1985): 328
  12. Davidson JM, Dellagrammatikas H, Parkin JM "Maternal azathioprine therapy and depressed haemopoiesis in the babies of renal allograft patients." Br J Obstet Gynaecol 92 (1985): 233-9
  13. Alstead EM, Ritchie JK, Lennard-Jones JE, Farthing MJG, Clark ML "Safety of azathioprine in pregnancy in inflammatory bowel disease." Gastroenterology 99 (1990): 443-6

References for breastfeeding information

  1. "Product Information. Imuran (azathioprine)." Glaxo Wellcome, Research Triangle Park, NC.
  2. Gardiner SJ, Gearry RB, Roberts RL, Zhang M, Barclay ML, Begg EJ "Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother-infant pairs." Br J Clin Pharmacol 62 (2006): 453-6
  3. Cerner Multum, Inc. "Australian Product Information." O 0
  4. United States National Library of Medicine "Toxnet. Toxicology Data Network. Available from: URL:" ([cited 2013 -]):
  5. Coulam CB, Moyer TP, Jiang NS, Zincke H "Breast-feeding after renal transplantation." Transplant Proc 14 (1982): 605-9
  6. Department of Adolescent and Child Health and Development. UNICEF. World Health Organization "Breastfeeding and maternal medication: recommendations for drugs in the eleventh Who model list of essential drugs. Available from: URL:" ([2003]):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.