18 children??

The Duggar kids planned a big Mother's Day surprise for their mom this year. But the surprise was on them when Michelle Duggar announced on the TODAY Show that they were soon to welcome an 18th sibling.

“We’re expecting!” the happy mother told TODAY co-host Meredith Vieira and the entire Arkansas clan. “Number 18!

“They didn’t know. My girls watch the calendar like a hawk. We just found out on Monday night.”

“On Monday night she brought one of the [pregnancy] testers in,” Michelle's husband Jim Bob added. “I wanted to bring it with me, but she wouldn’t let me.”

And baby, due around New Year’s Day, would make 20.

Joshua, the Duggars’ eldest son, said the news, two days before Mother's Day was “a shock” — if only to a point.

“I wasn’t expecting that,” the 20-year-old said. “But it’s been nine months [since the birth of the last baby], so yeah.”

Family forest
To date, the Duggars’ 17 natural children range in age from 20 years to 9 months. Included in the mix are 10 boys and seven girls — Joshua, twins Jana and John-David, Jill, Jessa, Jinger, Joseph, Josiah, Joy-Anna, twins Jedidiah and Jeremiah, Jason, James, Justin, Jackson, Johannah and baby Jennifer, who arrived last Aug. 2.

With two sets of twins, Michelle has gone through 15 pregnancies that ended in 13 natural deliveries and two Caesarean sections.

Both Michelle and Jim Bob — a former state legislator who served in the Arkansas House of Representatives — are real estate agents. They claim their family is debt-free, with the entire bunch helping to build their 7,000-square-foot home in Tontitown. And they are enriched by a devout faith in their religion.

The Duggars are followers of the evangelical Christian movement called Quiverful, which teaches that children are God’s blessing and that husbands and wives should happily welcome every child they are given. In fact, the Duggars' Web site, duggarfamily.com, quotes “Children are a heritage of the Lord” from verse 3 of the 123rd Psalm.

“We just let the Lord decide,” Jim Bob told Vieira.

“They are such a gift and we’re enjoying them so much,” Michelle added. “We would love more, and the power of the Lord took our faith to give us another one.”

The Duggars married in 1984, when Michelle was 17 and Jim Bob was 19. They held off on having kids for four years before Michelle ceased taking birth control pills to have their first child. After Joshua was born in 1988, Michelle returned to birth control but wound up getting pregnant anyway. Unfortunately, she suffered a miscarriage, which the couple attributed to use of the pill.

Michelle and Jim Bob decided to pray for as many children as God would give them. Within a year, Michelle was pregnant with the first of their two sets of twins.

Their large number of offspring has meant other large numbers for the Duggars. Michelle has been pregnant for 135 months of her life, with an average of 18 months between births. The family estimates it has used 90,000 diapers and launders 200 loads of clothes each month in a row of industrial-size washers and dryers.

Even though they go through three loaves of bread per day, they claim to feed their family for less than $2,000 a month. Transportation is facilitated by nine vehicles, led by a 21-passenger bus. They estimate that all members of the family have combined to work approximately 39,000 hours on their home.

Each child learns to play both violin and piano. And for what it’s worth, when child No. 18 arrives, they’ll have enough kids to field two baseball teams.

Most importantly, there is a unique dedication to serve the greater good of the home and family. An older child will take on the responsibility of a younger sibling throughout the day. The children help prepare meals and keep to a steady home-schooling schedule. Group studies include materials from Advanced Training Institute International, a Bible-based education program for families.

The Duggars' daily adventures are currently being chronicled in a television series on the Discovery Health channel. They previously participated in another Discovery Health series, “On the Road with 16 Kids."