She’s an aging MTV queen and he’s a 45-year-old boy band member – but Jenny McCarthy and Donnie Wahlberg are still determined to have a baby!

The 42-year-old newlywed and her husband are ready to let nature take its course – as sources confirmed to The ENQUIRER !

“Jenny knows that she might have a difficult time even conceiving,” a close pal of the couple said. “But she and Donnie talked it over, and decided to give it a shot!”

The “Playboy” pinup married the onetime New Kid on the Block back in August, and the celebrity couple already have three sons between them. Donnie is father to Xavier, 22, and 13-year-old Elijah – while Jenny has 12-year-old son Evan. Now the couple is dreaming of adding a daughter to their blended family.

“Jenny is such a girlie girl,” said the source. “She’d love to have a little girl around the house to shop for dresses and Barbie Dolls!”

The couple is particularly wary of fertility treatments, though. Jenny’s son – from her earlier marriage to John Asher – is autistic, and the former “View” host has been famously outspoken about her belief that vaccines may have been responsible for his condition.

“They are leaving things up to fate,” said the source. “They’re going to roll the dice – and are just hoping for the best for now!”