The FDA previously assigned letter categories to medications based on their potential for risk to the fetus. Categories(A, B, C, D and X) have been assigned to all drugs to help to quickly classify a drug for safe use during pregnancy.
Category A
Adequate and well controlled studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy. There is no evidence of risk in later trimesters.
Some drugs belonging to this category include;
- Thiamine, Folic acid, Pyridoxine
- Docusate, Senna, Bisacodyl
- Dextromethorphan
- Doxylamine
- Levothyroxine
Category B
Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well controlled studies in pregnant women
Some drugs belonging to this category include;
Antibiotics
- Penicillin V, Penicilline G Benzathine, Amoxicillin, Amoxicillin/Clavulanate, Ampicillin, Oxacillin
- Ceftriaxone, Cephalexin, Cefuroxime
- Clindamycin, Azithromycin, Erythromycin
- Metronidazole
Antimicrobials
- Clotrimazole
- Mefloquine
- Acyclovir, Famciclovir
- Amphotericin B
Antiemetics and other GI medications
- Metoclopramide
- Ondansetro
- Loperamide
- Lansoprazole, Pantoprazole
Analgesics and other meds
- Acetaminophen
- Meperidine
- Clozapine
- Benztropine
Category C
Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well controlled studies in humans, but potential benefits may warrant use of the drug in pregnancy woman despite potential risks.
Category D
There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in human, but potential benefits may warrant use of the drug in pregnant woman despite potential risks
Some drugs belonging to this category include;
- Gentamicin
- Doxycycline, Tetracycline
- Fluconazole
Category X
Studies in animals or humans have demonstrated fetal abnormalities and there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the risks involved in use of the drug in pregnant woman clearly outweigh potential benefits.
Some drugs belonging to this category include;
- Griseofulvin
- Oxytocin
- Ribavirin
- Emergency contraception: Levonorgestrel, Ulipristal
Note: Not all medications belonging to these groups are captured
