My experience is maids cannot be trusted. My maid has worked for me for 6 years and has got married. When she renewed the 4th contract with me last year, she said she wanted to earn more money for another 2 years and then retired. When I asked her more (of course, bits by bits indirectly), she said she would like to take holiday for 4 weeks and her husband would also be back at that time. Her husband wanted to get a baby during that time. If she was pregnant, she would not return. So, you see, they are very selfish, never consider how it will affect you and the family.
I have finally asked my maid to get the injection or I won't renew the contract with her. Injection can be for 1 month or for 3 months. I insist my maid to get the 3 months as she takes vacation for 4 weeks (1 month will be riskly). It costs about HK$300-400 and I pay for it. You can check the price with any clinic.