Ondansetron (Zofran) and Ketorolac Safety in Pregnancy
Ondansetron is safe and effective for use in pregnancy as a second-line antiemetic, while ketorolac is contraindicated in labor and delivery and should be avoided, particularly in late pregnancy.
Ondansetron (Zofran)
Ondansetron can be used safely during pregnancy when first-line antiemetics fail. The most recent 2024 BJOG guideline explicitly states that ondansetron use as a second-line antiemetic should not be discouraged if first-line agents are ineffective 1.
Key Safety Data:
- Orofacial cleft risk: There is a very small absolute risk increase from 11 cases per 10,000 births (background) to 14 cases per 10,000 births with first-trimester ondansetron exposure 1
- This minimal risk should be balanced against the significant morbidity of poorly managed hyperemesis gravidarum
- Multiple large studies including over 97,000 first-trimester exposures show no overall increase in congenital malformations 1
Supporting Evidence:
Recent high-quality research confirms safety:
- A 2021 multinational cohort study of 456,963 pregnancies found no association between ondansetron and fetal death, spontaneous abortion, stillbirth, or major congenital malformations (adjusted HR 0.91,95% CI 0.67-1.23) 2
- A 2013 Danish cohort of 608,385 pregnancies showed no increased risk of adverse fetal outcomes 3
- A 2022 meta-analysis found ondansetron was actually associated with reduced miscarriage risk (OR 0.53,95% CI 0.31-0.89) 4
FDA Classification:
The FDA labels ondansetron as Pregnancy Category B, with animal studies showing no teratogenicity, though adequate human studies are limited 5.
Ketorolac
Ketorolac should be avoided during pregnancy, particularly in late pregnancy, and is absolutely contraindicated during labor and delivery.
Critical Contraindications:
The FDA drug label explicitly states: "The use of ketorolac tromethamine is contraindicated in labor and delivery because, through its prostaglandin synthesis inhibitory effect, it may adversely affect fetal circulation and inhibit uterine contractions, thus increasing the risk of uterine hemorrhage" 6.
Pregnancy Risks:
Ketorolac is Pregnancy Category C with the following concerns 6:
Maternal effects near term:
- Prolonged gestation and labor
- Increased peripartum blood loss
- Increased anemia
Fetal effects near term:
- Premature closure of ductus arteriosus
- Pulmonary hypertension
- Impaired renal function and reduced urine output
- Reduced amniotic fluid volume
- Increased cutaneous and intracranial bleeding
General NSAID Guidance:
The 2009 American Family Physician guideline confirms that while NSAIDs are not known to be teratogenic, they should be discontinued 6-8 weeks before term 7. Women actively trying to conceive should avoid NSAIDs as they may block blastocyst implantation 7.
Clinical Algorithm
For nausea/vomiting in pregnancy:
- Start with first-line antiemetics: antihistamines (promethazine, cyclizine), phenothiazines, or doxylamine/pyridoxine 1
- If ineffective, advance to ondansetron as second-line therapy 1
- Counsel patients about the minimal orofacial cleft risk (3 additional cases per 10,000) balanced against HG complications 1
For pain management in pregnancy:
- Avoid ketorolac entirely during pregnancy when possible
- Never use ketorolac in the third trimester or during labor 6
- If NSAID use is necessary early in pregnancy, use lowest effective dose for shortest duration and discontinue by 32 weeks gestation 7
Important Caveat:
The one study showing ketorolac use immediately after oocyte retrieval in IVF had no detrimental effects 8, but this represents a very specific, limited exposure scenario that does not apply to ongoing pregnancy use.