JOHN EDWARDS and his mis­tress RIELLE HUNTER are keeping a startling baby secret – the couple has made the shocking decision to have another child!

That’s what sources tell The ENQUIRER as the 58-year-old dis­graced former presidential candidate prepares for his federal trial in April.

“Rielle’s biological clock is ticking loudly and she’s desperate to have an­other baby with John,” a source close to the 48-year-old blonde divorcee told The ENQUIRER.

“She’s not sure what the future holds for John, and that’s made her even more de­termined. She wants to get pregnant before the trial begins.

“She’d love to have another sibling for their daughter Quinn.

“And John, who loves children as much as she does, is on board with the baby plan – and it’s given him even more impetus to win his trial and not go to prison.”

Edwards’ career and personal life ex­ploded after he was exposed as a cheater by a series of blockbuster ENQUIRER exclusives beginning in 2007. After ve­hement denials, he was finally forced to admit paternity of Quinn, now 4, before his wife Elizabeth lost her heroic battle with breast cancer on Dec. 7, 2010.

The affair also sparked major le­gal woes for Edwards. Last June, he was indicted by a federal grand jury on six felony charges that he illegally used campaign funds to cover up his extra­marital affair.

If convicted, the former senator faces a maximum 30 years in jail and $1.5 mil­lion in fines. He denies doing anything illegal.

Last June, The ENQUIRER revealed that Rielle dumped Edwards just days before he was indicted, and sources said she would testify against him at trial.

But Rielle has now forgiven him, say insiders, and she rushed to his side after a frightening heart condition delayed the start of his trial.

ALL the details are in the NEW ENQUIRER!