Evan hasn't been in a real womb for months, not to mention never had to pass his head through a tight passage... which is why it was a normal shape from the get-go.
TRANSCRIPTION COURTESY OF JOSEPH HOUK - [Medical City Hospital; CW is getting her "post-birthing" exam] (Doctor, voiceover) "Everything looks great for your new bundle of joy. He's in good health!" (CW, voiceover) "Yay for that!" (Doctor) "And what's amazing is your baby's head looks normal already! Was it really hard for you to pass that?" (CW, uncertain) "Yyyyeah, it was!" (Doctor) "That must've roughed you up down there. Let me check for any vaginal tearing…" (CW, who's REALLY not sure what to do now) "Er… Uhh…" [KNOCK KNOCK] (Doctor Garcia, who's not holding a stethoscope in his hand) "Excuse me, Doctor, I need your immediate opinion on this specimen. Can you follow me to the lab?" (Doctor) "Um… Okay! Excuse me for a moment!" [Off-screen – CW knows what's happening when she hears the FZZAP] (Dr. Garcia, returning with a nurse – who's apparently also "in the know" – holding Evan) "Okay, Cassie, you're good to go! We'll get a birth certificate printed and sent to you as soon as we can!" (CW) "Uh, thanks!" (Dr. Garcia, to "Doctor Keith") "Sorry I'm late. Traffic was horrible and I don't have a time machine like you!" (KS, rolling his eyes like this isn't the first time he's heard that) "Garcia, there's a reason those aren't standard-issue…"