Lucy Puryear, M.D., author of Understanding Your Moods When You're Expecting

Pregnancy

FDA Drug Categories for Use in Pregnancy

CATEGORY	INTERPRETATION
A	Adequate, well-controlled studies in pregnant women have not shown an increased risk of fetal abnormalities to the fetus in any trimester of pregnancy.
B	Animal studies have revealed no evidence of harm to the fetus, however, there are no adequate and well-controlled studies in pregnant women.
	OR
	Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.
C	Animal studies have shown an adverse effect and there are no adequate and well-controlled studies in pregnant women.
	OR
	No animal studies have been conducted and there are no adequate and well-controlled studies in pregnant women.
D	Adequate well-controlled or observational studies in pregnant women have demonstrated a risk to the fetus. However, the benefits of therapy may outweigh the potential risk. For example, the drug may be acceptable if needed in a life-threatening situation or serious disease for which safer drugs cannot be used or are ineffective.
X	Adequate well-controlled or observational studies in animals or pregnant women have demonstrated positive evidence of fetal abnormalities or risks. The use of the product is contraindicated in women who are or may become pregnant.
Source: Physicians Desk Reference, 60th ed. (Montvale, NJ: Thomson PDR, 2006).

Examples of Medications Used in Pregnancy

Class A: Thyroid hormone.

Class B: Wellbutrin (bupropion, antidepressant). Although this drug is classified as a Class B drug, there are fewer studies of the effects of this drug during pregnancy than many of the Class C drugs. It is not necessarily safer.

Class C: Prozac (fluoxetine, antidepressant), Zoloft (sertraline, antidepressant), Celexa (citalopram, antidepressant), Lexapro (escitalopram, antidepressant), Effexor (venlafaxine, antidepressant), Cymbalta (duloxetine, antidepressant).

Class D: Paxil (paroxetine, antidepressant), lithium carbonate (mood stabilizer for bipolar disorder). Paxil has been shown to have a small increased risk of a commonly treatable heart defect when taken in the first trimester. Lithium carries an increased risk of Ebstein’s anomaly, a more serious heart defect involving the tricuspid valve.

Class X: Thalidomide (anti-miscarriage drug).

Lucy Puryear
author of
Understanding Your Moods When You're Expecting:
Emotions, Mental Health, and Happiness -- Before, During, and After Pregnancy