I grew up with aunts and uncles who gave me jewelry as gifts so it was normal in my family. If your niece is still wearing the necklace you gave her for graduation then her husband must know the story behind it...and hopefully he wouldn't find it strange that you are gifting her jewelry for the birth of their child. I think it's a really thoughtful gesture but try to make sure that it is her taste and not yours or her husband's. My mother-in-law gave me a nice ring as a push present for the birth of my first daughter and it was totally her taste and not my style at all. Although I was really touched and appreciated the gift, I only wore it when she was around and when I didn't, she would ask about it. 😳 It's been years since I last put it on but it is a treasure that I will keep as a sweet memory of my daughter's birth.