The 31-year-old revealed that the pregnancy came as a shock, because doctors had previously told her she wouldn't be able to conceive again.
Explaining how she managed to fall pregnant so quickly after the birth of her second son last July, Jennifer joked:
"You don't think you have to be super careful with contraception when you're told you can't conceive."
Jennifer is due to give birth in September, and while she is excited about the new arrival, she did admit she would like a longer gap before having baby number four.
"I'll wait four or five years before I have any more," she told OK! magazine. " I'll get back in shape, get my varicose veins done and sort myself out!"
Jennifer and her husband Robbie Tickle already have two sons, four-year-old Bobby and 11-month old Harry.
The former Brookside actress is eager is find out the gender of her third child and is hoping for another boy.
"My friends are throwing me a 'gender reveal' baby shower," she said. "It's where you cut into a cake and the sponge will either be pink or blue, and that's how you find out the sex."
This isn't Jennifer's first 'surprise' baby. She only discovered her second son Harry was on the way when she was four months pregnant. Speaking to us exclusively about her fertility worries she said:
"The word the doctors used was 'unlikely'. I have suffered with cysts on my ovaries which made it difficult to conceive. We knew we wanted another baby, but we were told it might not happen for us naturally."