"This Mother's Day is definitely going to be different because we'll be at the hospital," she tells PEOPLE. "This is the first time I've been in the hospital on Mother's Day."
Josie was born on Dec. 10 at a gestational age of 25 weeks, weighing just 1 lb. 6 oz., after Michelle's preeclampsia (pregnancy-related high blood pressure) put both their lives at risk.
"She reached the 6 lb. mark today," says Michelle excitedly, adding that doctors continue to run tests to determine when Josie will be released. "We're going to have a six pounder party."
Meanwhile, husband Jim Bob and the 17 other kids at home are scrambling to get ready for Mother's Day themselves.
"The kids and I went out shopping but Michelle is hard to buy things for because she is so practical," he says.
"I just need a new cover for the ironing board," she says, laughing.
Oldest son Josh, 22 and his wife, Anna, 21 are planning to celebrate Mother's Day with the whole family, including their 6-month-old daughter Mackynzie and Jim Bob's mother, Mary Duggar.
"It's Anna's first Mother's Day and that's very special, too," says Michelle. Agrees Jim Bob, "Looks like we'll have three generations of moms here celebrating together."
Though their youngest daughter Josie is still in the hospital, Michelle is visiting with other moms about how grateful they feel. "I was just sitting with another mom and going over all the blessings," she says. "It could be a lot worse. Our babies are growing, that is not always the case."
Last month, Josie was released from the hosptial, only to be rushed back soon after. Her emotional homecoming will be featured in a TLC Mother's Day special 19 Kids and Counting: Josie Comes Home on Sunday, May 9 at 8 p.m. EST, and her trip back to the hospital will be shown on the show on Tuesday, May 11 at 9 p.m. EST.
"This is a very special Mother's Day even though we are going through a lot of unknowns," says Jim Bob. Michelle says she takes care not to ask the littler children what's happening, "because they will tell all the Mother's Day secret plans and the older kids will get upset."
"We are going to remember this Mother's Day like no other," Michelle says. "It will be a Mother's Day I remember forever."