The 30-year-old beauty - who has four-year-old daughter Harlow and two-year-old son Sparrow with husband Joel Madden - thought it would help her fellow 'Fashion Star' mentor prepare for motherhood if she took care of the youngsters for a while, but Jessica turned down the offer.
Asked if Nicole had offered any parenting advice to pregnant Jessica, she said: ''I offered [Jessica] to take my kids up until she has her. That didn't really work.
''The offer still stands because she hasn't had her kids yet. So, if she wants to take them, go ahead. No problem!''
When she isn't busy with her work or raising her children, Nicole loves to relax by watching reality TV show 'The Real Housewives of Beverly Hills' but insists it is not a ''guilty pleasure''.
She told 'Access Hollywood': ''Well, I don't feel guilty about it at all. So, I don't know if it's my 'guilty' pleasure, because I just love it ... I'm a big Lisa Vanderpump fan.''
Jessica and fiance Eric Johnson are due to welcome their first child into the world in the coming weeks.