(a) A permanent employee, or an employee holding a position by permanent or temporary appointment who requests leave because of pregnancy or childbirth, may, in the discretion of the department, be granted a leave of absence without pay for a period not exceeding two years. Any such leave of absence may be extended beyond two years, for periods aggregating not in excess of an additional two years, only with the approval of the Civil Service Commission. In an exceptional case, a further extension may be permitted by the commission for good cause shown and where the interests of the government would be served. For the purposes of this section, time spent in active service in the military forces of the United States or of the State of New York shall not be considered in computing the period of leave.

Where a leave of absence without pay has been granted for a period which aggregates two years, or more if extended pursuant to subdivision (a) of this section, a further leave of absence without pay shall not be granted unless the employee returns to his position and serves continuously therein for six months immediately preceding the subsequent leave of absence.

This section shall not be construed to require the extension of any employment beyond the time at which it would otherwise terminate by operation of law, rule or regulation.