TDap Vaccine

Kristina💙 • • wife • fur mommy • baby boy 06.22.16 •
My OBGYN told me that she wants me to receive my TDap vaccine AFTER delivery. (I'm 8w4d).My next appointment is in a few weeks & I was going to ask then, but would anyone know why they would want to wait to give me the shot? & has anyone had this happen to them before?
(Please refrain from "anti-vac" comments.)
Thank you!