How to Read Pregnancy and Lactation Labeling on Drugs

When you're pregnant or breastfeeding, taking any medication isn't just about what works-it's about what’s safe. For years, doctors and patients relied on simple letter categories: A, B, C, D, or X. But those letters didn’t tell the whole story. In 2015, the U.S. Food and Drug Administration (FDA) replaced them with something far more useful: the Pregnancy and Lactation Labeling Rule (PLLR). Now, instead of guessing what a letter meant, you get real data-numbers, timelines, and clear explanations. But reading this new format takes a little practice. Here’s how to make sense of it.

What Changed from the Old Letter System?

Before June 30, 2015, drug labels used five letter categories to summarize pregnancy risk:

• A: Human studies show no risk (less than 2% of drugs)
• B: Animal studies show no risk, but human data is limited (about 15% of drugs)
• C: Risk can’t be ruled out (about 70% of drugs)
• D: Evidence of human risk (around 10% of drugs)
• X: Contraindicated in pregnancy (less than 1% of drugs)

These categories were misleading. Many people thought A meant “perfectly safe” and X meant “never under any circumstances.” But that’s not how risk works. A drug labeled C could be safer than a B in some cases, depending on timing, dose, or underlying condition. The old system didn’t explain background risks-the fact that about 3% of all pregnancies have a major birth defect, and 10-20% of known pregnancies end in miscarriage. Without that context, the letters were meaningless.

The New PLLR Format: Three Clear Sections

The PLLR restructured drug labeling into three mandatory subsections under Section 8: Pregnancy (8.1), Lactation (8.2), and Females and Males of Reproductive Potential (8.3). Each follows the same simple structure:

1. Risk Summary - What we know about the risk
2. Clinical Considerations - What to do in practice
3. Data - How we know it

This format doesn’t just say “this is risky.” It tells you why, when, and how much.

Reading the Pregnancy Section (8.1)

The Pregnancy subsection starts by grounding you in reality:

Risk Summary often begins with: “The background risk of major birth defects in the U.S. general population is 2-4%.” Then it adds: “Exposure during the first trimester was associated with a 1.5-fold increased risk of neural tube defects.” That means if the baseline risk is 3%, the increased risk becomes about 4.5%. It’s not “dangerous”-it’s measurable.

Some labels specify timing: “Increased risk observed only with exposure between weeks 4 and 10 of gestation.” That’s critical. If you take a drug after week 10, the risk may not apply. Others note if the risk is dose-dependent: “Risk rises with daily doses above 500 mg.”

Clinical Considerations gives you actionable advice. Examples:

• “Consider switching to a safer alternative before conception.”
• “Monitor fetal anatomy with targeted ultrasound at 18-22 weeks.”
• “Avoid use in the third trimester due to risk of neonatal withdrawal.”

Data shows the science behind the claims. You’ll see things like:

• “Prospective cohort study of 1,200 pregnancies (95% CI 1.2-1.9)”
• “Registry data from 2018-2023, including 347 exposed pregnancies”
• “No controlled trials; based on observational data”

This helps you judge the quality of the evidence. Was it a small, poorly controlled study? Or a large registry with long-term follow-up?

Understanding Lactation Labeling (8.2)

Breastfeeding concerns are often ignored. The PLLR changed that. The Lactation section now includes:

• Drug levels in breast milk - Measured as a percentage of maternal dose. For example: “Infant exposure is estimated at 4% of the maternal dose.”
• Potential effects on the infant - “No adverse effects reported in 85 breastfed infants.”
• Monitoring recommendations - “Observe for drowsiness or poor feeding in infants during the first two weeks.”

Many drugs pass into breast milk-but not all cause harm. A drug with 10% infant exposure might still be safe if it’s poorly absorbed by the baby’s gut. Others, like certain antithyroid drugs, can affect infant thyroid function even at low levels. The label tells you what to watch for.

Some labels now include pharmacokinetic data: “Peak milk concentration occurs 1-2 hours after maternal dose.” That means timing your dose right after feeding can reduce infant exposure.

Reproductive Potential Section (8.3)

This section matters even if you’re not pregnant right now. It includes:

• “Pregnancy testing recommended prior to initiation and monthly during treatment.”
• “Effective contraception required; failure rate of 9% with typical use of oral contraceptives.”
• “Potential for reversible infertility with prolonged use.”

For example, drugs like isotretinoin (Accutane) or certain chemotherapy agents require strict pregnancy prevention plans. This section ensures you’re not just told “don’t get pregnant”-you’re told how to prevent it, and with what level of reliability.

How Clinicians Are Adapting

A 2018 study found 62% of obstetricians struggled with the new labels at first. Why? Because they had to read paragraphs instead of scan a letter. But over time, confidence grew. By 2022, 73% of perinatal specialists preferred the narrative format for complex cases.

Pharmacists report a big shift too. A 2021 survey showed 64% of pharmacists now get more questions from patients about pregnancy risks. And 78% say they spend 5-7 extra minutes per prescription counseling. That’s time well spent. Patients who understand the real numbers feel more in control.

Some clinicians still rely on external tools. The TERIS and MotherToBaby databases are now used by 80% of primary care providers for pregnancy-related prescribing decisions. These are free, evidence-based, and updated monthly.

What You Should Do

If you’re pregnant, planning to become pregnant, or breastfeeding:

• Ask your provider: “Can you show me the pregnancy and lactation section of this drug’s label?”
• Don’t rely on old advice. A drug labeled “C” ten years ago might now have detailed data showing low risk.
• Check if your medication is listed in a pregnancy exposure registry. There are 47 active registries tracking drugs like antidepressants, antiseizure meds, and biologics. Participation helps future patients.
• Use the FDA’s free PLLR Navigator app to search drug labels on your phone.

Remember: a higher risk number doesn’t always mean “don’t take it.” Sometimes, the risk of not treating your condition-like uncontrolled seizures, depression, or high blood pressure-is far greater than the drug’s risk. The new labels help you weigh both.

What’s Coming Next

The FDA is working on visual aids-icons that show risk levels at a glance. Draft guidance from 2023 proposes symbols like:

• 🟢 Low risk
• 🟡 Moderate risk
• 🔴 High risk

These will appear alongside the narrative text. By 2025, the FDA plans to update 100% of pregnancy-related drug labels. And starting in 2022, all new drugs must include lactation pharmacokinetic data-how much enters breast milk, when it peaks, and how long it lasts.

Still, gaps remain. A 2023 report found 63% of psychiatric drug labels lack specific gestational timing details. And only 15% of registry participants are Black or Hispanic, even though those groups make up 30% of U.S. pregnancies. That’s something regulators are now trying to fix.

Final Takeaway

The old letter system gave you a shortcut. The new system gives you clarity. It doesn’t tell you what to do-it tells you enough to make a smart choice with your provider. You’re not just reading a label anymore. You’re reading science.