Why Does a Pregnant Mother Experiencing Stress Run the Risk

Why does a pregnant mother experiencing stress run the risk of providing less oxygenated blood to her baby?

A) Stress can cause the mother to put on weight, which causes the child to get less oxygenated blood during digestion.
B) Stress can cause the umbilical cord to reduce in diameter, making it difficult for blood to "get through."
C) Stress causes the hormone cortisol to be released, and this hormone is teratogenic.
D) Stress can cause blood to flow to body parts affected by the fight-or-flight symptom, thus reducing its availability to the child.