12.—(1) Where the date of confinement of a pregnant employee occurs in a week after the expected week of confinement, the minimum period of maternity leave shall be extended by such number of consecutive weeks (subject to a maximum of four consecutive weeks) after the week in which the date of confinement occurs as ensures compliance with section 10.

(2) Where the minimum period of maternity leave is proposed to be extended under this section, the employee concerned shall—

( a ) as soon as practicable after the proposal for such extension, notify in writing her employer (or cause her employer to be so notified) of the proposed extension; and

( b ) as soon as practicable after the date of confinement, confirm in writing to her employer the notification under paragraph ( a ) and specify the duration of the extension.