Last Updated on January 9, 2026
Quick definitions: Categories A, B, C, D, and X
In the old FDA letter system, each letter described the kind of pregnancy safety data available and what that data suggested.
People often search “pregnancy class b” or “pregnancy class c,” but these labels refer to the old pregnancy risk categories, not drug types.
- Category A: Human studies did not show fetal risk in early pregnancy, and later risk is not expected.
- Category B: Animal studies did not show fetal risk, or animal risk was not confirmed in human data.
- Category C: Risk cannot be ruled out. Human studies are lacking, and animal data may show risk.
- Category D: There is evidence of fetal risk in humans, but benefits may outweigh risks in serious situations.
- Category X: Risks clearly outweigh any possible benefit in pregnancy. Use is contraindicated.
If you want to see the legacy definitions in one place, the U.S. government’s CHEMM resource summarizes the categories here: FDA pregnancy categories overview.
What “pregnancy class” means and why it gets confusing
When someone says “pregnancy class C,” they usually mean the old Category C labeling, not a medication class.
Medication classes pregnancy searches often point to categories like “antibiotics,” “SSRIs,” or “opioids.” The A/B/C/D/X letters were different: they were a risk-labeling shortcut.
Why the letters were easy to misread
The letters look like grades, so many people assume A is “safe” and X is “dangerous.” That is not how clinical decision-making works.
The letter was partly shaped by what data existed, not only by how risky the medicine truly was.
Why you still see the letters today
Even though the system has been phased out for new prescription labeling, older references, older medication guides, and some online summaries still show the letters.
That is why people still encounter phrases like pregnancy category d or pregnancy category x when reading older sources.
If you are searching these labels because alcohol or drug use is part of the picture, you may need added medical support. Structured care options like inpatient rehab in Wimberley can help people stabilize and plan next steps with a clinical team.
What the letters do not tell you
The letter system leaves out details that often matter most in pregnancy care.
Two medications with the same letter can have very different real-world risk profiles.
- Trimester matters. Some risks are highest early in pregnancy, while others increase later.
- Dose matters. A higher dose can mean higher exposure and different risk.
- Route matters. Topical, inhaled, and oral products can lead to different absorption levels.
- Your health matters. Untreated illness can also harm pregnancy outcomes.
- Evidence quality matters. “No data” is not the same as “no risk.”
A key nuance about Category C
Category C is especially common in older labeling. It often signals limited human data, not a proven problem.
That is why “pregnancy class c” can be stressful to read, even when the real risk is uncertain rather than confirmed.
What replaced A/B/C/D/X on modern drug labels
The FDA replaced the letter categories with a narrative labeling approach called the Pregnancy and Lactation Labeling Rule (PLLR).
The goal is to support clearer, more clinically useful counseling, instead of relying on a single letter.
FDA overview: Pregnancy and Lactation Labeling Resources (PLLR)
What you’ll see under PLLR
- Pregnancy: risk summary, clinical considerations, and available supporting data.
- Lactation: information about drug levels in breast milk and possible infant effects.
- Females and males of reproductive potential: pregnancy testing, contraception, and fertility details when relevant.
FDA’s plain-language explanation of why the letters were removed: Questions and Answers on the Pregnancy and Lactation Labeling Rule
How to use category information safely in real life
If you see an A/B/C/D/X letter in a summary, treat it as a starting point for questions, not an answer.
A safer approach is to ask for specifics about evidence, timing, alternatives, and your personal risk factors.
A practical checklist to discuss with a clinician
- Confirm the goal of the medication and what happens if the condition goes untreated.
- Ask what human pregnancy data exists and what outcomes were studied.
- Ask whether risk changes by trimester or dose.
- Review safer alternatives, including non-drug options when appropriate.
- Check for interactions with other prescriptions, supplements, alcohol, or nicotine.
- Make a plan for monitoring, follow-up, and any warning signs that need urgent care.
If withdrawal is involved, do not go it alone
Some substances and medications carry serious risks if stopped suddenly, especially during pregnancy.
If you are dealing with dependence, medically supervised support may be the safest route. Learn more about Austin detox as a starting point for stabilization and care planning.
Examples of how categories are commonly misunderstood
Misreading categories can lead to two risky extremes: stopping needed treatment abruptly or dismissing real fetal risk.
These examples show why context matters more than the letter alone.
“Category D means you must never use it”
Not always. Pregnancy category d indicates evidence of fetal risk, but it also recognizes that benefits may outweigh risks in serious conditions.
This is a clinician-led, case-by-case decision, not a self-decision made from a letter grade.
“Category X means the medication is always ‘the most dangerous’”
Pregnancy category x means the risks outweigh any benefit in pregnancy, so it is contraindicated for pregnancy use.
It does not mean it is “more harmful” than every D drug in every situation. It means the benefit case is not there for pregnancy.
“Category B means it’s proven safe”
Pregnancy class b often reflects limited human pregnancy data. It can be reassuring, but it is not a guarantee.
Clinicians still consider timing, dose, and your health needs.
When medication is part of addiction treatment
Some people research A/B/C/D/X because they are reading about medications used in addiction recovery.
If you need structured support that includes medication and counseling, medication-assisted treatment (MAT) can be part of a broader plan, guided by qualified medical professionals.
When to get help now and where to start
If you are pregnant and worried about medication exposure, do not wait until anxiety builds into a crisis.
Bring your full medication list to a clinician, including over-the-counter products, vitamins, and supplements.
If substance exposure is part of the concern
Pregnancy can raise the stakes around alcohol, opioids, benzodiazepines, stimulants, and other substances, especially when dependence is present.
If a baby is exposed to certain drugs in the womb, newborn withdrawal can occur after birth. Nova’s educational guide explains signs and treatment options for newborn withdrawal symptoms (NAS).
Building a safer plan for the next 90 days
For many families, the best next step is a structured treatment plan that reduces chaos and increases medical oversight.
If you need a higher level of care, explore Austin residential inpatient rehab to understand how intensive support can fit into a recovery path.
