MIRANDA LAMBERT shocked coun­try music fans when she sud­denly announced she’s taking a break from touring – but The ENQUIRER learned there’s a surprising secret behind her decision.

She’s finally agreed to have a baby with hubby Blake Shelton, say insiders. Still, there’s apparently a troubling reason for their family plans.

Although a rep for the couple insists their union is strong, a close source claims: “Miranda had run out of options for sav­ing her strained marriage. It’s like they were one step away from divorce court.

“Blake has been begging for a baby forever, and Miran­da finally gave in. She’s telling friends that she’s actively trying to get pregnant right now.

“She hopes to be able to announce some happy news by midsummer, which would be perfect timing because her last shows are scheduled for mid-September. So she won’t be showing during her swan-song concerts.”

Meanwhile, the source adds that it’s a dream come true for “The Voice” coach Blake. But Miranda’s baby promise doesn’t come without strings attached.

“Miranda warned Blake that bringing a child into their lives means she’s adopting a zero-tolerance policy about his boozing, carousing and flirt­ing,” explained the source.

“She told Blake that she’ll up and leave, with their baby in tow, if he slips up even once.”

The 30-year-old “Au­tomatic” singer, who’s regularly toured since her debut album in 2005, announced in April that she’s di­aling back her concert schedule.

“She’s a workaholic,” said the source. “But when Miranda leaves Blake to his own devices, he tends to get into trouble.”

As The ENQUIRER report­ed, the couple – who celebrate their 3rd wedding anniversary this month – have fought bit­terly over Blake’s persistent wandering eye. Most recently, hot-tempered Miranda – who lost 35 pounds in a desperate bid to save her marriage – blew a gasket over her 37-year-old husband’s shameless flirting with 21-year-old “Voice” con­testant Audra McLaughlin.

Miranda has also seen red over Blake’s friendships with younger singers Cady Groves and Cassadee Pope.

Earlier this year, we revealed that a bitter divorce battle was looming over the couple’s combined $100 million fortune. Miranda was demand­ing that Blake check into rehab, and the country crooner was pushing her to have a baby, something she was hesitant to do so soon af­ter dropping the weight.

“In the end,” said the source, “Mi­randa realized that maintaining her fig­ure – or furthering her career – wasn’t as important as saving her marriage.”