The 35-year-old, who is mother to 18-month-old Xander, had her baby bump disguised in a storyline which saw her character, Betty Francis, put on weight because she was unhappy, reported Contactmusic.
"When we started filming, I was quite pregnant and had to come into work at 3am each day for six or seven hours of prosthetic make-up," she said.
Jones added she was afraid of the response to her changing appearance but was relieved when fans accepted it well.