The 31-year-old singer revealed during Thursday's episode of her VH1 reality show LeAnn and Eddie that she had been visiting doctors to have her fertility levels checked.
"[The specialist] told me that my levels are on the lower side of normal and that we should not be waiting very much longer," Rimes told Cibrian during the episode. "Does that freak you out?"
When Cibrian, who already has two kids -- Mason, 10, and Jake, 6 -- with his ex-wife Brandi Glanville, questioned whether the two are ready to have kids of their own, Rimes explained that while she's in no rush either, she does not "want to miss what possibly could be my only opportunity to have a child naturally."
Later in the episode, the "How Do I Live" singer reveals it wasn't easy for her mother to become pregnant with her and that she fears she might run into the same problem.
"I knew my mom had difficulty having me, but I never really knew how difficult it was," she said. "Eddie and I have talked about waiting a little bit longer before we try to have kids. It had never popped into my head that maybe I will have the same trouble she did."
The revelations about Rimes' fertility issues come almost two months after Life & Style reported the couple had "consulted with doctors" about in vitro fertilization.