The interincisal angle between deciduous incisors is:
Primary teeth are upright, but permanent teeth incline to the labial surface, thus decreasing the inter-incisal angle from about 150 degrees in the deciduous dentition to 123 degrees in the permanent dentition. This increases the arch perimeter.
 
Ref: Textbook of orthodontics Gurkeerat Singh 2nd ed pg no 46
100 degrees
120 degrees
150 degrees
170 degrees