I have a maternity dataset, where each mother has a record per pregnancy. I want to do two things:
1. Find the mothers with multiple pregnancies.
I do this by sorting the id's and generating a tag.
sort id
egen tag=tag(id)

2. Now I want to browse all the records for all the mothers that have multiple pregnancies.
Currently I do:

browse if tag==0 //to find the id's
browse if id==1 | id==4

Is there a more efficient way to do this? Maybe flag the id's that have a tag==0?
id tag
1 1
1 0
2 1
3 1
4 1
4 0
5 1
6 1
7 1
Would be grateful for any help.

Thanks,
Maria