Safety Of Medicines Taken During Pregnancy: 7 TGA Categories
Essential guide to understanding medicine risks during pregnancy, from fetal harm to TGA categories for safe prescribing.
Medicines and drugs can pose risks to the fetus if taken during pregnancy, potentially causing harm such as malformations or other adverse effects. They should only be used when the expected benefits to the mother clearly outweigh the risks to both mother and baby, using the lowest effective dose for the shortest duration.
Key Principles for Medicine Use in Pregnancy
The risks of fetal malformations are highest in the
first trimester
(first 12 weeks of gestation), when organogenesis occurs. Withdrawal effects on the newborn must be evaluated for medications like antidepressants taken in thethird trimester
(after 28 weeks). Rarely, paternal exposure, such as to finasteride, has been linked to issues.- Minimize exposure: Essential medicines only, lowest dose, shortest time.
- Timing matters: Avoid non-essential drugs in first trimester; monitor late-pregnancy use.
- Consult datasheets: Always check the most current approved drug datasheet for pregnancy-specific data.
Data on many medicines is limited, and classifications may change with new evidence. Health professionals should reference national resources like the Australian Therapeutic Goods Administration (TGA) Prescribing Medicines in Pregnancy database.
Pregnancy Risk Categories (TGA Classification)
Drug licensing authorities, such as Australia’s TGA, classify medicines into categories A-X based on pregnancy risk. These aid prescribing decisions but are not absolute—individual datasheets take precedence. Below are detailed definitions from TGA (accessed 2019, still foundational).
| Category | Description | Key Risks/Notes |
|---|---|---|
| A | Medicines taken by large numbers of pregnant women and women of childbearing age without proven increase in malformations or harmful effects on the fetus. | Safest category; no identified risks. |
| B1 | Limited human use without increased malformations; animal studies show no fetal damage. | Subcategory of B; human data limited but reassuring. |
| B2 | Limited human use without increased malformations; animal data inadequate or lacking, no evidence of fetal damage. | Human safety appears good; animal data insufficient. |
| B3 | Limited human use without increased malformations; animal studies show fetal damage of uncertain human relevance. | Caution advised; animal risks not confirmed in humans. |
| C | Pharmacological effects may cause harmful effects on fetus/neonate (e.g., neonatal depression) without malformations; effects often reversible. | Risk based on mechanism; not necessarily teratogenic. |
| D | Increased incidence of human fetal malformations or irreversible damage; adverse pharmacological effects possible. Not absolutely contraindicated. | Higher malformation risk; use only if benefits outweigh risks. |
| X | High risk of permanent fetal damage (teratogenic); absolutely contraindicated in pregnancy or possibility of pregnancy. | Never use; e.g., thalidomide causes severe birth defects. |
Note: Category B does not imply greater safety than C. Always cross-reference with FDA, MHRA, Medsafe, or local formularies like NZF, BNF.
Examples of High-Risk Medicines
Certain dermatological and common drugs exemplify these categories:
- Category X: Thalidomide—crosses placenta causing severe birth defects; strict contraception required for women of childbearing potential.
- Category D: Oral fluconazole (high doses >150 mg in first trimester) linked to spontaneous abortion and cardiac septal defects.
- Topical avoidances: Retinoids (tretinoin, adapalene), high-concentration salicylic acid for acne; dithranol for psoriasis.
- NSAIDs: Contraindicated after 28 weeks; short-term use before may be considered with caution.
Prescribing Considerations for Specific Conditions
Psoriasis Treatment
Many topical agents are safe, but avoid retinoids and dithranol. Safe options include topical corticosteroids (mild potency), calcipotriol (limited use), and emollients. Biologics/small molecules not routinely recommended due to insufficient data—see national guidelines.
Acne Management
Severe flares are rare but challenging. Safe topicals: azelaic acid, benzoyl peroxide (low concentration), erythromycin/clindamycin. Systemic isotretinoin is Category X—strictly contraindicated.
Over-the-Counter (OTC) Medicines
Avoid OTC where possible, especially first trimester. Paracetamol is first-line for pain/fever but avoid long-term. Codeine risks neonatal withdrawal near term. Decongestants, high-dose NSAIDs, and complementary medicines (CAMS) generally unsafe unless labeled safe (e.g., fish oil).
Special Populations and Scenarios
- Unplanned pregnancies: ~50% in NZ; pharmacists must screen for pregnancy before dispensing.
- Lactation: Separate considerations apply post-delivery; many dermatological meds safe but consult resources.
- Paternal exposure: Rare but possible (e.g., finasteride).
Resources for Healthcare Professionals
Primary references:
- Australian TGA Prescribing Medicines in Pregnancy database.
- New Zealand Formulary (NZF/NZFC).
- US FDA Pregnancy Categories (historical, transitioning to narrative).
- UK MHRA/BNF/BNFC.
- Medsafe datasheets.
Always verify with the latest datasheet, as classifications evolve.
Frequently Asked Questions (FAQs)
Q: Can any medicine be taken safely in pregnancy?
A: Category A and some B medicines have the strongest safety data. All others require risk-benefit assessment; consult TGA/NZF.
Q: What if I took a Category D or X drug accidentally?
A: Contact your doctor immediately for ultrasound/fetal monitoring. Early intervention possible for some risks.
Q: Are topical creams safer than oral medicines?
A: Often yes, due to lower systemic absorption, but avoid retinoids/salicylates. Emollients and mild steroids preferred.
Q: Is paracetamol safe throughout pregnancy?
A: Yes for short-term use; avoid regular/long-term due to potential effects.
Q: What about herbal or complementary medicines?
A: Generally avoid; limited evidence, risk of contaminants. Only use labeled safe products.
Conclusion for Prescribers
Pregnancy alters pharmacotherapy profoundly. Prioritize non-drug measures, then safest agents. Multidisciplinary input (obstetrician, dermatologist) essential for chronic conditions like psoriasis. Patient education on contraception for teratogenic drugs is critical.
References
- Safety of medicines taken during pregnancy — DermNet NZ. 2023-01-01. https://dermnetnz.org/topics/safety-of-medicines-taken-during-pregnancy
- Fluconazole – OK to use in pregnancy? — Medsafe (NZ Govt). 2020-12-01. https://www.medsafe.govt.nz/profs/PUArticles/December2020/Fluconazole-use-in-pregnancy.html
- Community pharmacy guide on medicine safety in pregnancy — bpac NZ. 2019-01-01. https://bpac.org.nz/2019/otc.aspx
- Treatment of Psoriasis in Pregnancy — DermNet NZ. 2023-01-01. https://dermnetnz.org/topics/treatment-of-psoriasis-in-pregnancy
- Thalidomide — DermNet NZ. 2023-01-01. https://dermnetnz.org/topics/thalidomide
- Acne in Pregnancy — DermNet NZ. 2023-01-01. https://dermnetnz.org/topics/acne-in-pregnancy
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