Wash. Rev. Code § 26.26A.510
(4) In a proceeding under RCW 26.26A.400 through 26.26A.515, a copy of a bill for genetic testing or prenatal or postnatal health care for the woman who gave birth to the child and the child, provided to the adverse party not later than ten days before a hearing, is admissible to establish:
[ 2018 c 6 s 522.]