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!