Sacrifice by S.J. Bolton

Sacrifice - Tora Hamilton and her husband, Duncan Guthrie recently moved to the Shetland Islands.  Duncan grew up on the islands but Tora is considered an outsider.  When her horse, Jamie died, Tora decided to bury him on their land.  While she was digging the grave, she came across the corpse of a woman who had recently gave birth and had her heart removed.  An obstetrician, Tora wants to know what happen.  However, the only person who seems to care is Detective Sergeant Dana Tulloch, herself an outsider.  The investigation of the two women lead them to a mysterious maternity hospital on a nearby island that registers only a few births every year.