Heidi Montag struggled to contain herself in Costa Rica last week -- when the reality star's bikini top happened to collapse under the pressure of a G-cup-sized breast ... right in front of the cameras.
Spencer Pratt's loving wife is known for taking things too far.
Heidi Montag -- Oops, My Boob Fell Out!
9/14/2010 7:00 PM PDT BY TMZ STAFF
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