Drug Test

I'm just curious as to if your OBGYN drugs tests. Mine makes me pee in a cup every time I go so I figured the answer to me own question is yes. But just curious if anyone knows for sure? Long story short, my little sister is pregnant as well as me, and she use to fool around with weed and I'm not sure if she's kicked the habit yet. I don't want her to get into any trouble, but I would like to know if she's doing it to the baby.