What is the pregnancy category of Sevoflurane (sevoflurane) in a pregnant patient?

Sevoflurane Pregnancy Category

Sevoflurane does not have an FDA pregnancy category assigned because the FDA eliminated the letter category system (A, B, C, D, X) in 2015, but based on the current FDA labeling, sevoflurane would have previously been classified as Category B—indicating no adequate and well-controlled studies in pregnant women exist, though animal studies have shown some adverse effects only at high doses. 1

Current FDA Labeling Information

The FDA label for sevoflurane explicitly states: "There are no adequate and well-controlled studies in pregnant women." 1

Animal Study Findings

The safety profile is based primarily on animal reproduction studies:

• At low doses (0.3 MAC): No adverse fetal effects were observed in pregnant rats 1
• At high doses (1.0 MAC): Reduced fetal body weights and skeletal variations (delayed ossifications) occurred, but only in the presence of maternal toxicity 1
• In rabbits: No adverse fetal effects at any dose tested (0.1-1.0 MAC) 1

Understanding the Classification Context

The traditional FDA pregnancy categories are defined as follows 2, 3:

• Category B: Animal studies show no fetal risk but no controlled human studies exist, OR animal studies show adverse effects not confirmed in human studies
• Category C: Animal studies show adverse effects with no adequate human studies available
• Category D: Evidence of human fetal risk exists, but benefits may outweigh risks
• Category X: Contraindicated due to proven fetal abnormalities

Sevoflurane fits Category B criteria because animal studies at therapeutic doses showed no harm, and the adverse effects seen only occurred at supratherapeutic doses with maternal toxicity. 1

Clinical Use During Pregnancy

Documented Human Experience

• Sevoflurane has been used in 29 women for elective cesarean section with no untoward effects in mother or neonate 1
• Case reports document successful use during early pregnancy (13 weeks gestation) for non-obstetric surgery with normal infant delivery 4
• Limited pilot studies show effectiveness for labor analgesia without apparent maternal or fetal complications 5

Important Safety Considerations

Critical warnings from the FDA label include:

• Uterine relaxation: Sevoflurane can cause uterine smooth muscle relaxation and may contribute to uterine atony 1
• Neurotoxicity concern: Prolonged exposure (>3 hours) during peak brain development may increase neuronal apoptosis, though clinical significance remains unclear 1
• Safety in labor not established: The FDA explicitly states that "the safety of sevoflurane in labor and delivery has not been demonstrated" 1

Comparative Context with Other Volatile Agents

Guidelines indicate that volatile anesthetic agents (sevoflurane, isoflurane, desflurane) are largely cleared by exhalation with minimal placental transfer, making them relatively safe options when general anesthesia is required 2

Animal studies comparing sevoflurane to isoflurane in pregnant sheep showed that low-dose concentrations (0.5-1.0 MAC) of sevoflurane maintained uterine blood flow and fetal oxygenation, though high concentrations (1.5-2.0 MAC) caused hemodynamic instability 6

Practical Clinical Guidance

When sevoflurane use is necessary during pregnancy:

• Use the lowest effective concentration, ideally 0.5-1.0 MAC 6
• Limit exposure duration when possible, particularly avoiding prolonged exposures >3 hours 1
• Monitor for uterine atony, especially during cesarean delivery 1
• Be prepared to manage potential uterine relaxation with uterotonics 1

The absence of a formal FDA pregnancy category reflects the 2015 regulatory change, not increased risk—sevoflurane's safety profile based on available data would have warranted Category B classification under the old system. 1