The seven teams averaged 4,493 fans per game -- within the league projections of 4,000 to 6,000 for Year 1 -- but were hit hard by the downturn in economy.
In an interview with the St. Louis Post-Dispatch, Antonucci said losses in some cases were twice what were projected.
In a conference call with media on Tuesday, she explained that the losses were mostly due to drops in revenue projections -- in particular, local sponsorship income.
(WPS kept costs at minimal levels, mindful of the millions its predecessor, the WUSA, had burned through in its first season.)
"Keeping our eye on the ball and having long-term sustainability is extremely important to our league," said Antonucci.
She was hopeful improving economic conditions would allow teams to generate more sponsorship dollars. She added they needed to boost other income areas such as camps and clinics.
While she saw "no signs" of owners pulling out, she left the door open for some clubs to move to new stadiums in Year 2.
Three teams -- Sky Blue FC, Washington and Saint Louis -- played in two or more facilities in 2009. Gold Pride FC downsized its seating capacity at Buck Shaw Stadium after drawing only small crowds early in the season.
Saint Louis (3,833), FC Gold Pride (3,667) and Sky Blue FC (3,651) fell below the minimum goal of 4,000 set by the league.
WPS will expand to nine teams in Year 2 with the addition of Philadelphia and Atlanta.
WPS signed the U.S. Coast Guard as a presenting sponsor of its All-Star Game on Aug. 29.