As a baby delivered at 20 - 22 weeks can survive the limit for abortions should be below 20 weeks.
To allow for mistakes in dates maybe 16 - 18 weeks would be a sensible limit.
having had babies at 24 and 26 weeks i agree it should be lower and only in circumstances where there is extreme deformity should it be any lower, and even then only in extreme cases, not just in cleft palate as in the news recently.