Britney's little sis enjoys an intimate party with family and friends.

Friends and family of JAMIE LYNN SPEARS (including big sis BRITNEY) celebrated the 17-year-old's impending motherhood with a baby shower on Saturday! According to People, a party of 30 guests gathered for the ladies-only affair at the Spears' family's Serenity mansion in Kentwood, La.

"Jamie Lynn opened every gift," a source tells the mag. "We all sat in a circle and she opened gifts and thanked every person. It was just a good old fashioned baby shower."

Mother LYNNE SPEARS and fiancé CASEY ALDRIDGE's mother's were also on hand for the festivities, which made for "a wonderful, sweet occasion," the mag's source adds.