Maternity pay
A. The level of pay that a woman is entitled to under statutory maternity arrangements is calculated by looking at their earnings during the eight-week period prior to what is known as the qualifying week. (The qualifying week is the 15th week before a woman’s expected week of childbirth).
This assessment of their earnings must include their salary, as well as any overtime, commission and bonus payments. The inclusion of these additional payments can lead to significant discrepancies as pregnant employees who receive an annual bonus during their reference period will be better off than colleagues who do not.
In the situation you describe, your members will be entitled to the benefit of the pay rise that you have negotiated. The decision of the European Court of Justice in Alabaster v Woolwich plc C-147/02 established this point — a decision which was later incorporated into UK law by the 2005 Statutory Maternity Pay (General) (Amendment) Regulations.