I've never heard of a foreign maid kidnapping a child. If you read the Chinese tabloid press, they sometimes highlight cases of bad behavior - but I feel they cherry-pick the most horrendous cases. Given there are 300,000 maids here, of course some will be bad. But most are good, honest, and often quite loving of their charges.
In 15 years, I've never heard of family, friends or colleagues whose children were misstread by maids. A Filipina spent 15 years caring for my grandmother. Many of my cousins, who have young children, become attached to their Filipina or Indonesian helpers.
Some of my friends have not had perfect relationships with their maids -- sometimes disagreements over conditions, leave or pay. But I've never heard of anyone's children being misstreated.
You have to find someone you trust, regardless of nationality. Hiring carefully and checking references are more important than their race.
Are you pregnant now? Or are you moving to HK with a child?
If you are pregnant, I recommend that you get the maid in place a month or two before you deliver. That gives you time to suss her out and train her. You can spend, say, two months before delivering, and two months after. In four months, you should be able to tell if someone is trustworthy. And, at the end of the day, there are no guarantees in life -- and sometimes you just have to trust someone.
None of my family have ever used a Chinese long-term nanny. Mostly, they use the Chinese just for the first few months, as a "pu yuet." This is partly because they are expensive, and partly because they work fewer hours and do less work. Also, some have rather bossy personalities!
I used a Chinese nanny occasionally -- like on Sundays, when my helper was off, and I sometimes had to work. Or when my maid was back in the Philippines. I used this agency: bamboos.com.hk