不合理
如果我是你,建議你和老板還有hr一起談。
1 you need to point out that you will do your best to help out during January heavy loaded work and try to do maternity leave as late as possible, with condition it is safe for you to work, both hr and your manager should be agreed together with you.
2. You need to ask the payment being agreed regarding your sacrifice for holidays, be signed and countersigned. With condition that the baby will arrive on time.
3. If the baby arrives earlier than your last day, who shall be responsible for you? I mean you start maternity leave right before labour, are you sure? Most people start four weeks before.
4. Agree the date you return in front of hr.
Don't argue, try to explain your worries and difficulties.
Best luck.