Oprah Winfrey does not look out for her own ... at least that's what is alleged in a new lawsuit in which a female exec at OWN claims she lost her job because she got knocked up.

According to a lawsuit filed Friday, Carolyn Hommel claims she was hired in 2010 as senior director of scheduling and acquisitions at Oprah's OWN network. Hommel claims she was told she was on-track to become a VP, but says things took a sudden turn when she became pregnant.

According to Hommel ... her duties were slowly transferred to a temporary employee and she was excluded from meetings when she returned from medical leave. Hommel claims she was let go ONE MONTH after giving birth and told to re-apply for the VP gig ... only to be passed over.

Furthermore, Hommel claims her boss, Michael Garner, fabricated a performance review that "made Hommel's job duties and responsibilities appear less 'senior' and therefore not a candidate for the new vice president position."