"Actions speak louder than words" is a common saying that means your actions tell the truth even if what you say does not. She said she wasn't preganant, yet her "contractions speak louder than words". Contractions are when the uterine muscles become shorter. Contractions happen before the birth of the baby happens. We see the word "action" in "contractions". "Contractions speak louder than words" is supposed to share similarity with "actions speak louder than words". 
She said she wasn ' t pregnant but contractions speak louder then words .