Did anyone get the Tdap shot around 34 weeks?

I was reading up on the Tdap vaccine and read it is recommended at 28-36 weeks but should be given closer to the 28 week range. My doctor never mentioned this to me and I just had my 32 week appointment yesterday. I see her in 2 weeks when I will be 34 weeks and I plan to ask for it then but am a little worried as to why it’s recommended to be given earlier than that? Is it just not as effective the farther along you are?