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Phenytoin Pregnancy and Breastfeeding Warnings

Phenytoin is also known as: Di-Phen, Dilantin, Phenytek, Phenytoin Sodium, Phenytoin Sodium, Extended Release, Phenytoin Sodium, Prompt

Medically reviewed by Last updated on Nov 21, 2018.

Phenytoin Pregnancy Warnings

Administration of this drug to pregnant animals resulted in teratogenicity (increased incidences of fetal malformations) and other developmental toxicity (including embryofetal death, growth impairment, and behavioral abnormalities) in multiple animal species at clinically relevant doses. There are no controlled data in human pregnancy.

-An increased risk of congenital abnormalities ("fetal hydantoin syndrome") has been associated with the use of phenytoin (the active metabolite of this drug) in epileptic women during pregnancy.
-The overall incidence of neonate malformations for offspring of mothers treated with anti-seizure medications is approximately 10%, or 2 to 3 fold the incidence in the general population (although a definite causal relationship has not been established).
-Prenatal exposure to this drug may increase the risks for congenital malformations and other adverse developmental outcomes. Increased frequencies of major malformations (such as orofacial clefts and cardiac defects), minor anomalies (dysmorphic facial features, nail and digit hypoplasia), growth abnormalities (including microcephaly), and mental deficiency have been reported among children born to epileptic women who took this drug alone or in combination with other antiepileptic drugs during pregnancy.
-There have been several reported cases of malignancies, including neuroblastoma, in children whose mothers received phenytoin during pregnancy.

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.

This drug should not be used during pregnancy unless the benefit outweighs the risk to the fetus.

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

-If this drug is used during pregnancy, or if the patient becomes pregnant while taking the drug, the patient should be informed of the potential harm to the fetus.
-An increase in seizure frequency may occur during pregnancy because of altered phenytoin pharmacokinetics.
-Periodic measurement of plasma phenytoin concentrations may be valuable in the management of pregnant women as a guide to appropriate adjustment of dosage.
-Postpartum restoration of the original dosage will probably be indicated.
-Neonatal coagulation defects (reversible with vitamin K administration) have been reported postpartum.

See references

Phenytoin Breastfeeding Warnings

Use is not recommended.

Excreted into human milk: Yes

-Because of the low levels of this drug in breastmilk, amounts ingested by the infant are small and usually cause no difficulties when used alone except for rare idiosyncratic reactions. Breastfeeding during monotherapy does not appear to adversely affect infant growth or development.
-Combination therapy with sedating anticonvulsants or psychotropics may result in infant sedation or withdrawal reactions.
-In one case report, maternal phenytoin dosage requirements decreased as breastfeeding was discontinued.

See references

References for pregnancy information

  1. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. Available from: URL:" ([2006]):
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. "Product Information. Dilantin (phenytoin)." Parke-Davis, Morris Plains, NJ.

References for breastfeeding information

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. Available from: URL:" ([2006]):
  3. "Product Information. Dilantin (phenytoin)." Parke-Davis, Morris Plains, NJ.
  4. United States National Library of Medicine "Toxnet. Toxicology Data Network. Available from: URL:" ([cited 2013 -]):

Further information

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