(1) Subject to this section, where an employee has given notification of his or her intention to take parent's leave and his or her employer is satisfied that the taking of the parent's leave at the time specified in the notification would have a substantial adverse effect on the operation of his or her business, profession or occupation by reason of -

(a) seasonal variations in the volume of work concerned,

(b) the unavailability of a person to carry out the duties of the employee in the employment during the period of the leave,

(c) the nature of the duties referred to in paragraph (b),

(d) the number of employees in the employment or the number thereof whose periods, or parts of whose periods, of parent's leave will fall within the period specified in the said notification, or

(e) any other relevant matters,

the employer may, by notice in writing given to the employee not later than 4 weeks before the intended commencement of the leave, postpone the commencement of the leave to such time, not later than 12 weeks after the date of commencement specified in the relevant notification, as may be agreed upon by the employer and the employee.