Power Play by Anne McCaffrey

This final volume of the trilogy that began with Powers That Be opens with the marriage of Yanaba Maddock, administrator of the sentient planet Petaybee, to geneticist and selkie Sean Shongili. The pregnant Yana soon has to travel off-world to defend Petaybee's interests before a skeptical galaxy, leaving the planet open to devious exploitation by such predators as old enemy Torkel Fiske. The narrative shifts focus between the primitive but honest planet and the glittering space city of Gal Three as travails mount at both locations. Yana and two young friends are kidnapped by pirate Onidi Louchard; pilgrims and treasure seekers flood Petaybe.