I think you have to apply early as it is difficult to find a maid to take care new born BB now.
in my case, BB was born in Nov 2008, i sent the application form in June, then my maid arrived in HK in Sept. then i can have 2 months time to see whether she is ok or not. if she is no good, then i still have time to change a new one.
Mine now is 2.5 months before my EDD. I also suggest to hire the maid at least 2 months in advance. Also, check if1. you have your mom to train/take care you during your pregnancy period, even a bit late to hire her, your mom can help to train her,
2. you are a full time / business mama, if full time, u have more time to train her
3. if not fit for you, then you still have time to chance another one