A term of the woman's work that provides for maternity-related pay to be calculated by reference to her pay at a particular time is, if each of the following three conditions is satisfied, modified as mentioned in subsection (5).
The first condition is that, after the time referred to in subsection (1) but before the end of the protected period—
The second condition is that the maternity-related pay is not—
The third condition is that the terms of her work do not provide for the maternity-related pay to be subject to—
The modification referred to in subsection (1) is a modification to provide for the maternity-related pay to be subject to—
A term of her work that—
is modified so as to provide for her to be given it in circumstances in which it would normally be given.
Pay is within this subsection if it is—
A term of the woman's work that—
is modified so as to provide for it to be subject to the increase.
Maternity-related pay is pay (other than statutory maternity pay) to which a woman is entitled—
A reference to the protected period is to be construed in accordance with section 18.