Al Pacino was so certain he could not get his girlfriend or anyone else pregnant, he did not believe the baby was his at first, and got a DNA test for proof ... sources with direct knowledge tell TMZ.
The 83-year-old actor, we're told, had medical issues that would have commonly prevented a man from impregnating a woman. We're told Al had no idea until 2 months ago that 29-year-old Noor Alfallah was pregnant, and when he found out he was "shocked."
Our sources say Al doubted at first the baby was his and wanted a DNA test. We're told Noor obliged and the test showed he was indeed the dad.
Showbiz 411 first reported the paternity test.
TMZ broke the story ... Noor is 8 months pregnant. It will be Al's 4th child.