Thank you for your query.
The uterine artery
carries the blood flow to the pregnant uterus
Resistance to the blood flow indicates that there is slight obstacle in blood flow to the uterus, and hence to the baby.
Diastolic notching indicates an early problem in this regard.
It could be due to placental pathology or maternal diseases like hypertension
If the resistance increases, then the baby is at risk of compromise, and you might be scheduled for an elective cesarean section.
Your obstetrician would monitor the baby with serial colour dopplers.