Sacrifice / S.J. Bolton.

Enhanced descriptions from Syndetics:

In this masterful debut that starts off as a mystery and becomes much more, Tora Hamilton is an outsider at her new home on the rocky, wind-swept Shetland Islands, a hundred miles from the northeastern tip of Scotland. Though her husband grew up here, it's the first time he's been back in twenty years. Digging in the peat on their new property, Tora unearths a human body, at first glance a centuries-old bog body, interesting but not uncommon. But realizing that the body is in fact much newer, that the woman's heart has been cut out and that she was killed within a few days of bearing a child, Tora, herself an obstetrician, becomes obsessed with finding out what happened to her--even when the police, her colleagues and eventually her husband warn her against getting involved.

Reading town records and researching local lore, Tora discovers a disturbing link to ancient Shetland legend and uncovers a collection of deep, dark secrets---the kind of secrets worth killing for.

Sacrifice is a bone-chilling, spell-binding debut that will grip readers from its beginning to its startling end.