1/ "9月底的预产期。因此邀请国内母亲首次来英探亲照顾。"
I hope you didn't disclose this information on your invitation letter, and didn't use it as your reason to invite your mum to England. Did you do that?
Answer: Unfortunately I did do that.Is it the key reason for refusal?
2/ "6月初在广州签证处递交的申请，遭拒（大概因为我申请的是一年多次往返签证）。"
In good practice, when your mum's visa was denified, the officer would give exact reason. What was it? "大概因为我申请的是一年多次往返签证" is only your guess. It shouldn't be used as an excuse not to award your mum's visa. If your mum is not sure of the reason, she can ring them to find it out.
Answer: Actually,the reason is as following:
(1). I note that you have applied for entry clearance for a period of one year as a family visitor. This has been confirmed by your daughter in her invitation letter dated 23 May 2011. This category of visitor is not covered by the Immigration Rules and therefore fails to be refused under paragraph 320(1) of these rules.
(2). You have indicated on you visa application form that you wish to travel to the UK to look after your grandson for a period of one year. I accept that there are policy provisions for the short term care of relatives; however I consider that in your circumstances, what you propose to do constitutes employment, either paid or unpaid. This is not permitted for visitors to the UK. Furthermore you have not indicated who will care for your relative when you leave, or indeed what further care provisions will be in place for them. You have not provided satisfactory evidence of your own personal and financial circumstances. I have taken into account the reason for your proposed travel on this occasion,however I am not satisfied that this should outweigh my other concerns as indicated above. I am not satisfied that you do not intend to take employment in the UK or, in view of the fact that both you and your daughter have stated that you will remain in the UK for a period of one year, that you are genuinely seeking entry as a visitor for a limited period not exceeding six months, or you intend to leave the UK at the end of your visit.
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Based on the reasons above, I think i reapply (i)if I change my mum's one-year stay period to no more than six months in UK;(ii)if I do not disclose that my mum will come to look after my newborn baby;(iii)if my mum can provide satisfactory personal and financial circumstances.Are these can be helpful for get a visa for UK?
Thanks a lot!