Mad Men star January Jones says filming was tough during pregnancy

Actress January Jones poses at the 3rd Annual Coach Evening to Benefit Children's Defense Fun at Bad Robot on Wednesday, April 10, 2013 in Santa Monica, Calif. (Photo by Chris Pizzello/Invision/AP)

January Jones found filming 'Mad Men' tough when she was pregnant.

The 35-year-old actress - who is mother to 18-month-old Xander, but refuses to name the father - had her baby bump disguised in a storyline which saw her character, Betty Francis, put on weight because she was unhappy, and the beauty says each day's shooting was hard.

She explained: "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."

January added she was "afraid" of the response to her changing appearance, but found the reaction by fans was even better than she imagined.

She said: "I was very afraid of how that first episode would look when it aired, but I loved the audience response to her. When she's bigger, viewers are more sympathetic to her."

This season sees January's alter ego back to her pre-pregnancy figure and the actress loved slipping back into Betty's glamorous outfits.

She told Grazia magazine: "Betty's style has evolved, not only with time, but also with her role.

"In the first few years, she was emulating Grace Kelly, whereas now she sees herself as more of a Jackie Kennedy."