Brother my wife was pregnant when I get the medical. So what I did when got MR then immediately I informed my VO about the pregnancy and also anticipated date of delivery. So he informed me not to do medical now as I can do medical later with my wife after delivery of baby and can send all document which requested (i.e. PCC, Updated Information chart fresh passport bio pages) along with MR and Baby's additional documents. So I did what my VO suggested me to do. So after delivery I finish MR and then send all documents to LVO one time on 18/02/2015. So on 09/03/2015 they added my daughter in my application and sent MR for baby. Which I finished on 15/03/2015.
I suggest you to wait for your MR. when you receive it, then immediately inform your VO about pregnancy so he will give you time to finish the MR along with baby's documents.
LVO is asking below mentioned documents normally for baby,
Documents for your new baby:
Processing fee of $150
2 passport photos
Long form birth certificate
Copy of passport biopage
New Proof of Fund (as no. of family members increased)