There are two issues with maternity insurance:
1. When will coverage start (the link above is good for that), most companies are 6, 10 or 12 months after you start the policy.
2. Will they cover all costs in FULL. giving birth in HK can be ery expensive if you want private rooms, etc... The policies that have 'limits' or 'caps' will not cover all expenses for a birth in HK - so read the fine print carefully.
Example costs: vaginal delivery, 3 days, private room, Matilda, doctors fees - can be around HKD 100,000. c-sections and emergency issues are a lot more. And this does not include all your pre-natal doctor visits, midwife visits, etc....
So please take care when deciding and be sure to check what is covered and up to what limit (if there is one).
Good luck!