Reported revenue rose 34% for the same period, although April fared worse than the first quarter of 2009, according to a statement released at the holding company's annual general meeting in Dublin.
It also noted that the PR, public affairs, and branding identity units had been affected although not as much as WPP's information, insight, and consultancy businesses. Advertising and media investment management were least affected by the economic challenges facing the company.
Revenue figures for these units were not released.
The company lost 4,300 employees, or 3.7% of its staff, during the first four months of 2009 - less than half of which left involuntarily. WPP noted that balancing staff costs and headcount will be a "short-term focus" for the rest of the year.
In 2008, WPP said that there a 10% increase in overall revenues for PR and public affairs for the first five months of the year, with the other business units also showing revenue increases.