Failure to join
The fetal foreface forms from separate skin pods, like a hand/palm down, thumb&5th finger will be lower lip, middle 3 come together as middle, nose openings &upper lips.
All by 35 days. If the 3 top pods don't join u have 1 or 2 sided cl. The palatal ridges grow together from a front & 2 sides by 9wks & failure=cp, & may nor have a cl.There is polygenic linkage & some segragation of pure cl from cp.