FDA Pregnancy Categories

Category A: Human Studies, Animal studies

Human Studies: Controlled human studies show NO risk in 1st trimester (and no evidence in later trimesters).

Animal Studies: No risk shown.

_{^{Safest. Possibility of fetal harm appears remote.}}

Category B: Human Studies, Animal studies

Human Studies: No controlled human studies available OR human studies show no risk.

Animal Studies: Animal studies show no risk OR animal studies show adverse effects not confirmed in humans.

_{^{Presumed Safe. Acceptable to use if clinically indicated.}}

Category C: Human Studies, Animal studies

Human Studies: No controlled human studies available.

Animal Studies: Animal studies show adverse/teratogenic effects OR no animal studies conducted.

_{^{Use with Caution. Give ONLY if potential benefits outweigh potential risks. (Default category for $>60\%$ of drugs).}}

Category D: Human Studies, Animal studies

Human Studies: Positive evidence of human fetal risk based on adverse reaction data or human trials.

Animal Studies: Adverse effects documented.

_{^{High Risk. Potential benefits may warrant use in life-threatening emergencies or severe disease where safer alternatives fail.}}

Category X: Human Studies, Animal studies

Human Studies: Positive evidence of human fetal abnormalities or risk based on human experience.

Animal Studies: Studies demonstrate clear fetal abnormalities.

_{^{ABSOLUTELY CONTRAINDICATED. The risk of use in pregnant women clearly outweighs any possible benefit.}}

Category A: examples

Folic Acid (at recommended doses)

Levothyroxine

Pyridoxine (Vitamin B6)

Category B: examples

Amoxicillin / Penicillins

Paracetamol (Oral)

Metformin

Loratadine

Heparin / LMWH

Category C: examples

Ciprofloxacin / Fluoroquinolones

Morphine / Codeine

Fluconazole

Amlodipine

Albuterol

Category D: examples

Phenytoin

Carbamazepine

Tetracyclines

ACE Inhibitors / ARBs (2nd/3rd Trimester)

Lithium

Category X: examples

Isotretinoin

Thalidomide

Methotrexate

Warfarin

Statins (Atorvastatin)

Misoprostol

Pregnancy

Replaces former pregnancy category section. Must include whether a Pregnancy Exposure Registry exists, a narrative summary of risk based on human and animal data, and clinical considerations (e.g., disease-associated maternal/embryo-fetal risk, dose adjustments during pregnancy, labor/delivery impact).

Lactation

Replaces "Nursing Mothers." Provides details on drug presence in human milk, effects on the breastfed child, and effects on milk production/secretion.

Females and Males of Reproductive Potentia

Focuses on clinical requirements for pregnancy testing, mandatory contraception before/during/after therapy, and potential impacts on infertility.

Anticoagulant Rule

Heparin / Enoxaparin (Category B) does NOT cross the placenta → SAFE in pregnancy. Warfarin (Category X) DOES cross the placenta → CONTRAINDICATED in pregnancy.

Hypertension in Pregnancy

Preferred antihypertensives for pregnancy-induced hypertension (PIH) or preeclampsia are Methyldopa (first-line classic), Labetalol, or Nifedipine. ACE inhibitors and ARBs are strictly Category D

Analgesic Selection

Paracetamol (Category B) is the drug of choice for pain/fever in pregnancy. NSAIDs (Mefenamic acid, Ibuprofen) are Category B/C in the 1st/2nd trimesters, but become Category D in the 3rd trimester because they cause premature closure of the ductus arteriosus and prolong labor

Default Category Rule

If an unfamiliar drug is presented on the board exam and you must make an educated guess between safety profiles, remember that the vast majority of market drugs fall under Category C