According to Spontaneous and induced fetal activity
Spontaneous motor activity of the foetus depends significantly ot the foetal age; during the period between the 12th and 16th week it was recorded in 94.4%
By spontaneous, correct me if I wrong, I understand non reflexive movement and by induced I understand reflexive movement, since
A reflexive reaction or movement occurs immediately in response to something that happens.
But also, according to this other article Fetal movement
purposive movement begins at about 18 weeks, gradually replacing reflex movements
If "spontaneous movement" it isnt reflexive movement since it isnt an automatic reaction to something, and it isnt purposive movement, what is it exactly, and what does it generate it?