First of all, congratulations!
Do you have medical insurance?
I have just returned to Arg. after many years abroad. I had my first ob/gyn appointment weeks ago, so I cannot recommend anyone.
Most of my friends are new moms, so I can ask around, but I first need to know which insurance company you are with.
One thing that I've noticed is that only 1 out of 6 friends did not have a C-section. If you are pro natural birth, just beware, since more and more obstetricians in Argentina (and the world) seem to love C-sections and epidural for the most ridiculous reasons.
I remember seeing an expat's blog about becoming a mom in Argentina, will paste the link if I find it.
Sorry if my writing is not warm, I am in a hurry and a bit out of touch with the language!
Good luck! Saludos,
M