'The Office' Star Ellie Kemper Secretly Welcomed Baby in September

Congratulations are in order for Unbreakable Kimmy Schmidt star Ellie Kemper, who revealed on Sunday that she and husband Michael Koman welcomed their second child in early September. The couple welcomed their son, whom they named Matthew, on Thursday, Sept. 5, just three days after Kemper had joked on social media about being "102 weeks pregnant."

"Happy 1-month Birthday to our baby boy, Matthew!" Kemper wrote alongside a photo of herself and her baby boy, whose face was not visible. "He has inherited his dad's brown hair and his mom's desire to be carried around all day in a baby sling. He's a good boy."

Matthew joins big brother James Miller Koman, 3, whom the couple welcomed in July of 2016.

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A post shared by Ellie Kemper (@elliekemper) on Oct 5, 2019 at 8:47am PDT

The news was met with a round of congratulations from the actress' 871,000 Instagram followers, including family and friends.

"So many congratulations to you and your family," one person wrote, adding that "Matthew must be a good sleeper as you look wonderful."

"Congratulations from Scranton!" the account for Access NEPA (Northeast Pennsylvania wrote, referencing her time on The Office.

"Awwww! So happy for you!" Kemper's former The Office co-star Angela Kinsey wrote. "Love you!!!"

"Congratulations to you and your beautiful family!," a third commented.

"Ellie! Congratulations!!!! His head is beautiful and you look stunning!!!" Busy Phillips wrote, to which Kemper responded by asking her to "please teach me everything you know about taking care of two kids bc I'm sort of overwhelmed."

The Office alum had announced that she was pregnant with her second child during a May appearance on Jimmy Kimmel Live!, during which she and cast members from the All in the Family and The Jeffersons television event about a party Kimmel had thrown. Kemper had missed the party because she was sick.

"It's because I'm pregnant, and I felt sick. ... I've been blaming the pregnancy on so many things, and this is one of them. I'm so sorry I wasn't there," she said, confirming news of her pregnancy to E! News in June.

Shortly after confirming the pregnancy, Kemper opened up about her "awful" first trimester during an appearance on Live With Kelly and Ryan.

"The first trimester was awful," she said. "I have a 2-year-old now and when I was pregnant with him, I was fine. First trimester [this time], just terrible! Just tired and nauseous and all of it."

At the time, Kemper also revealed that she and Koman were waiting to learn the sex of their baby.