Final answer:
Assessing maternal vital signs between contractions allows for relaxation and restoration of oxygenated blood flow to the fetus, ensuring maternal and fetal well-being.
Step-by-step explanation:
The best rationale for assessing maternal vital signs between contractions is to allow for a period of relaxation and restoration of oxygenated blood flow to the fetus. Each contraction reduces the flow of oxygenated blood to the fetus, so assessing vital signs during contractions would not accurately represent the maternal and fetal well-being. Fetal distress can occur if oxygenated blood is not restored to the fetus during the relaxation period between contractions.