The Terminator star wed journalist Shriver in 1986 and couple initially struggled to conceive.
Worried about her daughter's strong desire to start a family, Eunice Shriver, the sister of former U.S. President John F. Kennedy, reached out to the nation's top doctors for an explanation.
Her research led to questions about her son-in-law's ability to father kids and she feared his prolonged use of performance-enhancing drugs may have affected his ability to have children.
Schwarzenegger admits he was stunned when he learned his mother-in-law presented his wife with a complete medical report of her findings.
Recalling the drama in his new memoir, Total Recall: My Unbelievably True Life Story, he writes, "I just happened to see the report on Maria's desk, so I read it, and I was laughing my head off. (I told her,) 'Your mother is out of control.'"
Maria eventually fell pregnant with the couple's first child, Katherine, in 1989, and the pair went on to have four kids.