After suffering a heartbreaking miscarriage this January, Leah Calvert wanted to wait to try for another baby with husband Jeremy Calvert. But the star of MTV's Teen Mom 2 (born Leah Messer) got a happy surprise just months later!

As revealed on Us Weekly on Oct. 23, the 20-year-old mother to twins Aleeah and Ali, with ex-husband Corey Simms, is expecting her first child with Jeremy this winter. "There is a reason God gave the baby to us now," Leah tells Us in an exclusive issue in the new issue, out now.

"I'm not going to say it wasn't planned, because we intended to try -- eventually," she tells Us. "It just happened a little sooner than we expected. Our parents are thrilled. It'll be Jeremy's parents' first grandchild, so they're really excited."

After splitting from her first husband in April 2011, Leah, a stay-at-home mom, tied the knot one year later in June with Jeremy, a pipeline engineer, in Murrells Inlet, South Carolina.

While some critics say Leah is too young to have another child, the MTV star, who first appeared on season two of 16 and Pregnant, tells Us she's ready.

"The path I chose isn't right for everyone, but it's right for me," she explains. "I am financially stable -- we just bought our first home -- and I'm emotionally fit to have another child. I'm 100 percent prepared -- way more than I was at 16."

For more on Leah's baby joy -- and how her daughters are preparing to be big sisters -- pick up the new issue of Us Weekly**, on stands now.

This article originally appeared on Usmagazine.com: Teen Mom 2 Star Leah Messer: I Am "100 Percent Prepared" for Baby No. 3