What is a safe pain reliever for a woman in her third trimester of pregnancy?

Pain Relief in Third Trimester Pregnancy

Acetaminophen (paracetamol) is the only safe oral pain reliever for third trimester pregnancy, as NSAIDs are absolutely contraindicated after 28 weeks gestation due to risk of premature ductus arteriosus closure and oligohydramnios. 1, 2

First-Line Treatment: Acetaminophen

Use acetaminophen at the lowest effective dose for the shortest possible duration. 1, 3

Recommended Dosing

• 975 mg every 8 hours OR 650 mg every 6 hours orally 1, 3
• Maximum daily dose should not exceed 4 grams, though consider limiting chronic use to 3 grams or less daily to reduce hepatotoxicity risk 1
• Use only when medically indicated, not routinely 1, 4

Important Safety Considerations

• While acetaminophen remains the safest option, emerging evidence suggests associations between prolonged prenatal exposure (particularly >28 days or during second/third trimesters) and a 20-30% increased risk of neurodevelopmental outcomes including ADHD and autism spectrum conditions 5, 1
• The key is duration and cumulative exposure—short-term use for acute pain appears safer than chronic daily use 5
• Despite these concerns, acetaminophen remains recommended as first-line because alternatives carry more immediate and severe risks 1, 3

What to Absolutely Avoid in Third Trimester

NSAIDs (Ibuprofen, Naproxen, Ketorolac)

All NSAIDs must be discontinued after 28 weeks gestation. 1, 2

• Risk of premature closure of fetal ductus arteriosus 2
• Risk of oligohydramnios (low amniotic fluid) 2
• Risk of pulmonary hypertension in the newborn 2
• If inadvertently used, immediate discontinuation and fetal assessment for ductal constriction is necessary 2

When Acetaminophen Is Insufficient

For Severe Pain

If acetaminophen fails to control severe pain:

• Consider short-acting opioids at the lowest effective dose for the shortest duration 5, 3
• Morphine is the preferred opioid if strong analgesia is required 3
• Severe pain that doesn't respond to acetaminophen warrants medical evaluation for underlying complications 3

Non-Pharmacologic Approaches

Before escalating to opioids, try:

• Ice packs or heating pads 3
• Rest and positioning 3
• Physical therapy techniques 1

Critical Pitfalls to Avoid

1. Do not use combination products containing acetaminophen without accounting for total daily dose—easy to exceed safe limits 1

2. Do not withhold acetaminophen due to neurodevelopmental concerns when pain relief is medically necessary—untreated pain and fever pose their own risks 4, 6

3. Do not use NSAIDs "just for a few days" in third trimester—even brief exposure after 28 weeks carries serious fetal risks 2

4. Do not use aspirin in analgesic doses during pregnancy (low-dose aspirin for antiplatelet indication is different) 3

5. Avoid codeine-containing medications due to variable metabolism and risk of neonatal toxicity in ultra-rapid metabolizers 3

Practical Algorithm for Third Trimester Pain

1. Assess pain severity and cause—severe or unusual pain requires evaluation 3

2. Start with acetaminophen 650-975 mg every 6-8 hours as needed 1, 3

3. Add non-pharmacologic measures (ice, heat, rest) 3

4. If inadequate after 24-48 hours: Reassess for underlying pathology 3

5. For severe refractory pain: Consider short course of morphine with obstetric consultation 3

6. Monitor closely if acetaminophen use extends beyond a few days 5, 1