As standard, going on maternity or paternity leave should not negatively impact your building pension. Since you are still an employee and still receiving pay as such, your pension is not paused or stopped during this time. In fact, as you are still counted as an employee, your pension will continue to build during your maternity or paternity leave. However, it is worth noting that the amount will be based on your salary before you go on leave, rather than reflecting any salary increase that may happen during your leave or after it.