From Science Daily:
The putative skull of Saint Bridget (Birgitta) of Sweden that has been kept in a shrine in Vadstena Abbey is probably not authentic. A new study conducted at Uppsala University reveals that the two skulls, believed to be from Saint Bridget and her daughter Catherine (Katarina), are not from maternally related individuals. Furthermore, dating shows that the skulls are not from the time period when Bridget and Catherine lived.
Vadstena parish assigned Associate Professor Marie Allen's research group at Uppsala University's Department of Genetics and Pathology the task of examining DNA from both skulls, in order to confirm kinship and authenticity. A sensitive method based on analysis of the maternally inherited mitochondrial DNA was used to analyse the skulls. This method makes it possible to examine very small amounts of DNA, and it is often a successful analysis on aged and degraded material.