What nonsteroidal anti-inflammatory drug (NSAID), specifically Indomethacin, should be avoided in pregnant individuals after 32 weeks gestation?

Indomethacin Should Not Be Used in Pregnant People After 32 Weeks' Gestation

Indomethacin should be avoided in pregnant individuals after 32 weeks' gestation due to its significant risk of causing premature closure of the ductus arteriosus, which can lead to severe fetal complications including pulmonary hypertension. 1, 2

Risks of Indomethacin Use in Late Pregnancy

Fetal Cardiovascular Effects

• Indomethacin causes constriction of the fetal ductus arteriosus, with dramatic increase in risk after 32 weeks' gestation when the rate of compromise approaches 50% 3
• This constriction can occur rapidly - within 16-48 hours of administration 4, 5
• Consequences of ductal constriction include:
  • Pulmonary hypertension
  • Tricuspid regurgitation
  • Fetal hydrops (fluid accumulation in fetal compartments)
  • Potential need for surgical intervention after birth 6

Other Fetal/Neonatal Risks

• Increased risk of necrotizing enterocolitis (29% vs 8% in unexposed infants) 6
• Higher rates of intracranial hemorrhage (28% vs 9%) 6
• Renal dysfunction with decreased urine output and elevated creatinine 6
• Oligohydramnios (decreased amniotic fluid)
• Potential for prolonged or permanent renal failure 2

Safety of Other Medications in the Question

1. Vancomycin: Can be used throughout pregnancy when clinically indicated
2. Nifedipine: Can be used for hypertension and tocolysis throughout pregnancy 1
3. Nitroglycerin: Can be used when clinically indicated during pregnancy

NSAID Use Guidelines in Pregnancy

• NSAIDs (including indomethacin) are generally considered safe in early pregnancy 1
• All NSAIDs except low-dose aspirin (≤100 mg/day) should be discontinued after gestational week 32 1
• For pregnant patients requiring anti-inflammatory treatment after 32 weeks:
  • Low-dose prednisone may be used throughout pregnancy 1
  • Acetaminophen is allowed throughout pregnancy 1

Clinical Implications

• Indomethacin should be restricted to gestational ages <32 weeks when absolutely necessary 3
• If indomethacin must be used before 32 weeks, fetal echocardiography should be performed within 48 hours to monitor for ductal constriction 4
• Even short-term use (as little as 16 hours) can cause significant ductal constriction and pulmonary hypertension 5
• Effects may be reversible if the medication is promptly discontinued, but this should not be relied upon 4, 7

The American College of Rheumatology and the American Family Physicians explicitly recommend against using NSAIDs like indomethacin in the last 6-8 weeks of pregnancy (after 32 weeks' gestation) due to these significant risks 1.