California Code, Family Code - FAM § 7650

(a) Any interested person may bring an action to determine the existence or nonexistence of a mother and child relationship. Insofar as practicable, the provisions of this division applicable to the father and child relationship apply.

(b) A woman is presumed to be the natural mother of a child if the child is in utero after the death of the decedent and the conditions set forth in Section 249.5 of the Probate Code are satisfied.