Most people gasp at the prospect of having any more than three or four kids but for Michelle and Jim Bob Duggar, having children has never been about their own wishes but about God's.

After having 19 children together, you'd be forgiven for thinking the husband and wife team are ready to call it quits, but it seems they are happy for the pendulum to swing either way as they face up to the reality that Michelle's child-bearing years may be over.

A preview of this week's 19 Kids & Counting shows 47-year-old Michelle sharing about a recent visit to a fertility doctor and the results of blood tests.

"Conception is not totally impossible, but most unlikely," she says in the clip ahead of Tuesday night's episode of the TLC reality show, reports People magazine.

Jessa Duggar launches "Jessa Seewald" Instagram and Twitter accounts: Are they engaged?

The Duggars' youngest child is four-year-old Josie. They lost their 20^th child, Jubilee Shalom, to a miscarriage in 2011.

Jim Bob, 48, also appears in the clip and appears as faithful as ever about the future for his family and whether it will bring more children.

"We've always put this in Gods hands, and if God wants to give us more children, we are going to be happy either way."

It's a season for change in the Duggar household after Jill Duggar and Derick Dillard recently got engaged. They'll tie the knot on June 21.

Fans are waiting expectantly to see if Jessa Duggar and boyfriend Ben Seewald will also get engaged. They've been dating since last September.