"Human life must always be defended from its beginning in the womb and must be recognised as a gift of God that guarantees the future of humanity," Vatican Radio cited Francis as saying in a message to mark Brasil's National Family week.
The Argentinian pontiff's remarks came in the wake of a new law approved last week by Brasil's president Dilma Rousseff allowing its public healthcare system to administer the "morning-after pill" to rape victims.
Last month the pope went to Brazil on his first foreign trip as pontiff, drawing crowds of millions in various cities.
In Monday's message, Francis urged Brazilian parents to teach their children "the fundamental truths of life and human love" amid a "throw-away culture".
"Parents must convey to their children the knowledge that human life must always be defended, right from its onset in the maternal womb," the pope stated.