Final answer:
Reva Rubin's phase 3 of establishing a relationship with the fetus is known as the postpartum phase.
Step-by-step explanation:
In Reva Rubin's theory of establishing a relationship with the fetus, phase 3 is known as the postpartum phase. This phase refers to the period after childbirth where the mother and baby continue to bond and adjust to their new roles and responsibilities. During this phase, the mother may experience physical and emotional changes as she recovers from labor and delivery and begins breastfeeding.