What is the preferred treatment for seizures during pregnancy?

Magnesium sulfate is the preferred treatment for seizures during pregnancy primarily because of its effectiveness and safety profile. It is commonly used to manage seizures associated with eclampsia, a serious condition that can occur in pregnant women characterized by high blood pressure and seizures. Magnesium sulfate acts as a central nervous system depressant and can help stabilize the mother's condition while also providing neuroprotection for the fetus.

In contrast, the other options present concerns for use in pregnant patients. Phenobarbital can cause sedation and has potential risks to the developing fetus, including fetal dependence. Valproic acid is associated with significant teratogenic effects and is not recommended during pregnancy due to its association with congenital malformations. Diazepam, while effective for seizure control, is not favored in pregnancy as it may lead to sedation and respiratory depression in both the mother and the newborn.

Thus, magnesium sulfate stands out as the safest and most effective option for managing seizures during pregnancy, particularly in cases of eclampsia.