To use previously unused paid holidays as maternity paid leave.
The company I work for offers maternity leave, however it's not really used by employees. In my case, I plan to use previously unused paid holidays as maternity paid leave which will allow me to take a month off from work.
ご質問ありがとうございます。
この場合は、「過去の余った有休を育休として復活させる」と言えます。
また、「会社に育休制度はあるがまだ社員の中に利用者はほとんどいない。過去の余った有休を育休として復活させることで1ヶ月ほど休みを取るつもりだ。」と言ったいなら、これでも英語にしましょう。
下記の英文通りになります。
The company I work for offers maternity leave, however it's not really used by employees. In my case, I plan to use previously unused paid holidays as maternity paid leave which will allow me to take a month off from work.
ご参考になれば幸いです。
アメリカ合衆国 
