Ensure you have had a review of current targets before you leave and agree a date for setting new targets when you return from leave.
If you are currently in the PDP programme ensure that you have discussed any targets before your leave and agree with your manager how your 3 and 5 year reviews will be dealt with.
It may be appropriate to discuss reduced targets if you have a significant period of time out of the workplace, see the Exeter Academic web pages for further information. The quality, however, is not reduced.
If an employee takes maternity leave before they have completed their probation period, the maternity leave will pause the probation period. Ensure regular meetings carry on throughout their pregnancy and ensure they are aware that the probation period will continue after they return from maternity leave. Once they have returned ensure that meetings are scheduled in so work can be monitored within the probation period. If you have any concerns about performance speak to your HR contact immediately.