Final answer:
Calcium channel blockers are the first-line agents for high blood pressure in pregnancy.
Step-by-step explanation:
The first-line agents for high blood pressure (BP) in pregnancy are calcium channel blockers (CCBs).
CCBs are a class of medications that work by blocking the entry of calcium into the smooth muscles of the blood vessels, resulting in vasodilation and lowering of BP. They are considered safe and effective for use in pregnancy.
Examples of CCBs commonly used in pregnancy include amlodipine and nifedipine.