Jessica Simpson found out she was pregnant thanks to pre-cocktail "guilt".

The 31-year-old 'Fashion Star' mentor - who is expecting her first-born with fiancé Eric Johnson - admits she was overcome by bad feelings as she prepared for a drinking session.

She said: "We were going to have an all-day drinking binge. Going to ride our bikes, hang out ... do naughty things. But I started feeling this overwhelming guilt. Why would I feel guilt at the idea of going out and having cocktails with my friends?"

A pregnancy test confirmed her suspicions, and Jessica is expected to give birth to a baby girl this spring.

But the 'Dukes of Hazzard' actress - who was previously married to singer Nick Lachey - is praying her daughter inherits her sense of style.

She told Elle magazine: "I swear I will croak if she asks me for a pair of Nikes instead of Christian Louboutins!

"Eric is so athletic. We're going to have this athletic girl and I won't even be able to take her shopping."

The tabloids have targeted Jessica for her fluctuating weight in recent years, but the fashion designer insists she doesn't let it bother her because she is made of tough stuff.

She explained: "I'm still standing. I grew up very strong! "You know, my father used to be an adolescent therapist. I remember sitting at his office, watching the girls walking in and out. Kids doing coke at 16 ... heroin. Pregnant at 14. I could see what I didn't want to be."