The Duggar family is celebrating the announcement of eldest son Josh and wife Anna's pregnancy.

The "19 Kids & Counting" family reached out to fans via their Facebook page, and asked for prayers and support.

"Well, many of you have asked lately about another Duggar baby....and the word is officially out now that Josh and Anna are having baby #4!!!!" the family wrote on Wednesday.

"We are so excited for them and for our family as a whole. Every life is precious and designed with purpose and a God-given destiny. Rejoice with us and please pray for Anna and the baby in the months to come!! Yeah!!!"

On Tuesday, Anna revealed that she is nine weeks pregnant, and has experienced a lot of morning sickness.

"It's difficult, but it's good because I know that good things are happening," she said.

The pregnancy is Anna's first since the couple moved to Washington DC, and Josh discussed how their new surroundings make this pregnancy unique.

"The whole support group that we had in Arkansas, we don't have here," he explained. "We've made a lot of friends and all that, but thinking of having a baby in DC is a lot different."

Back in Arkansas, Josh's mother, Michelle, was asking Facebook fans for tips on how to keep her 16 children still living at home occupied on rainy days.

"The weather is cold and rainy here today!" she wrote on December 1. "What are some of your favourite indoor activities with your children on days like this? I'd love to hear from you. Go!"

Over 700 people responded with ideas, including building a fort with blankets, watching a Christmas movie while eating candy canes and drinking hot chocolate, and playing with Lego.

Michelle expressed thanks for all of the responses.

"So many sweet and wonderful ideas were posted for fun indoor, cold-rainy day, time with your kids!" she said. "Thanks for sharing these. We will be using a few of them!!!"