WPP reported first quarter revenue rose 5.5% to $3.8B, including an 8.1% jump in PR and public affairs revenue to $353.7M boosted in part by acquisitions.

The London-based conglomerate said Burson-Marsteller and Cohn & Wolfe showed the strongest growth in the PR sector, which gained 6.8% on a constant currency basis but only 1.9% excluding acquisitions. WPP acquired Glover Park Group in November and Crowdverb, First Move (U.K.) and Phjoisranta (Finland) for its PR/PA operation in the first quarter.

CEO Martin Sorrell said the “pattern of 2012 looks very similar to 2010 and 2011” as both consumers and corporations continue to be cautious and risk averse, although major events like the Summer Olympics, U.S. presidential election and UEFA Football Championships in Europe will provide a revenue boost.

WPP’s advertising and media business reported 8.3% growth to $1.5B for the quarter, outpaced by its branding and identity, healthcare and specialist communications operations which rose 10.8% to just over $1B.

Sorrell said 2013 could be a “cloud on the horizon” as it lacks any major events of 2012 like the Summer Olympics or U.S. presidential election to boost revenues.

Sorrell said it seems more likely that President Obama will be re-elected but that he will have to confront an “intimidating” budget deficit while dealing with a Republican House and/or Senate.