Japanese Birth/Pregnancy gifts, traditions and folklore

*sigh* I think I ask a question at least once a month.

I googled "japanese birth traditions," "Japan birth folklore/superstition," "Japan pregnancy traditions," "Japan pregnancy", "traditional pregnancy gifts japan" and related terms and found a few useful links. I am looking for any information on the following:

1. Do the Japanese have some superstition regarding announcing pregnancy? Is there a specific month where it's OK to say, "I'm pregnant?" 

2. Is it OK to give gifts to the expectant mother? My understanding is that traditionally, gift-giving before the birth is unusual, as most wait until the child is born . If it's OK to give gifts, what gift items would be appropriate? 

3. What are the traditional 'cautions' a pregnant woman has to take -- foods she should eat or avoid, jobs or actions she should or shouldn't do, clothes, etc.? I understand there is some significance attached to the 5th month of pregnancy, although the searches I turned up pointed me to women using "iwata-obi".

Timeline is anywhere from modern to ancient/past tradtions and practices. :)

Thank you so much in advance!