pinkyrose: there are apparently different methods of calculating the trimester periods, but the most common one is to treat the 1st trimester as being the 1st 12 weeks.
As for babymoon, going to HK is definitely safe don't worry! You can tell your DH about my friend who in the FIRST trimester, already went to Thailand and UK. In the second, she's going to Japan and then nearing the third, she's going to UK again and then flying from UK to New York before coming back to Singapore! Her doctor said ok to all this.
I was so inspired by her, I'm going to the States for my babymoon too haha. Apparently the baby stuff there is alot cheaper, so am going for a mega shopping trip [IMG=http://www.singaporemotherhood.com/forumboard/clipart/happy.gif]