Ciara and Russell Wilson didn't let just ANYONE deliver their precious baby Sienna Princess last week -- the doc on the receiving end of the table is one of the most famous OB/GYN's in the country! 

According to Sienna's birth certificate, obtained by TMZ, she was born on April 28 at Cedars-Sinai Medical Center -- where all the big Hollywood babies go to leave the womb. 

The doc in charge of the delivery is Dr. Robert Katz -- who's known around town as the OB/GYN to the stars. In fact, he's been honored by stars like Halle Berry and Nicole Richie.

And now he can add Sienna Princess Wilson to his list of accomplishments! 

Congrats!