Jeffrey Immelt
Andrew Harrer| Bloomberg | Getty Images
The General Electric-Baker Hughes oil and gas combination and the telecom tie-up of Century Link for Level 3 made this month the biggest ever for announced M&A.
October surpassed even the epic dealmaking surge in January 2000, according to S&P Market Intelligence.
What does that mean for your money?
At least in the short term, we found that it's not great for your portfolio. CNBC PRO, using hedge fund analytics tool Kensho, ran the numbers on what happens during the month after the nine previous biggest M&A months of all time.
