Mich. Comp. Laws § 722.1006: Grant of initial custody.

Sec. 6.

After completion of an acknowledgement of parentage signed according to section 3(1) that complies with this act is filed with the state registrar, the mother has initial custody of the minor child, without prejudice to the determination of either parent's custodial rights, until otherwise determined by the court or otherwise agreed upon by the parties in writing and acknowledged by the court. This grant of initial custody to the mother does not, by itself, affect the rights of either parent in a proceeding to seek a court order for custody or parenting time.