The United States Conference of Catholic Bishops has posted a resource online for dioceses, parishes and others to use to bless unborn children and their families.
The "Rite for the Blessing of a Child in the Womb" includes prayers and instructions for blessing unborn babies, their expectant parents and their families. The blessing is available in English and Spanish and can be used during or outside of Mass.
The blessing is available on the USCCB website. It also will be published as an addendum to the church's Book of Blessings.