The qualifying period will be paused (rather than stopped) if you take:
In other cases if you take a break which is related to pregnancy or childbirth, or if you take maternity, adoption or paternity leave, you will be treated as if you have continued working in an assignment.
It is clear that as an agency worker you will not have to work for 12 consecutive weeks via the same agency to qualify for the right to equal treatment. It is possible for you to accrue the 12 weeks’ qualifying period over a much longer period of time and through more than one agency.