Oh baby! Lauren and Seth Stevenson of Dickinson, North Dakota, have just given Labor Day weekend a whole new meaning with the arrival of their third child, Henry Lee — born full-term and naturally on Sept. 1 — the exact same day as his siblings Axel Lee, 2, and Tommie Lee, 1.

And proud mama Lauren couldn’t be more thrilled: “We were all just full of excitement that our healthy baby arrived on the 1st,” she told TODAY over the phone. “We didn’t plan this at all,” she adds, “How we got that lucky, we just don’t know.”

Even Stevenson’s obstetrician, Dr. William Lowe, who has supervised the deliveries of over 7,000 babies over 50 years, was baffled by the rare occurrence. “The situation of babies being born one year apart for three consecutive years is that generally people do not get pregnant that quickly in order to be at due date by the next year,” he says via e-mail.

The Stevenson Family

The Stevenson Family

Lowe delivered all three babies at CHI St. Alexius Health in Dickinson. “[Lauren] was a joy to work with,” he says, adding, “it was an honor to participate in caring for her throughout the pregnancies, and allowing me to participate in such a happy situation.” He goes on to say, “I’m so glad all the babies were born healthy. They have so much to look forward to in the future.”

And, regarding the Stevenson family’s task of raising three little ones at once, Lowe is confident in the couple’s abilities: “Being young helps a lot,” he says. “Often when deliveries are so close, [moms] have barely had time to recuperate from the last delivery — it’s very exhausting taking care of three babies all 2 years old or less.”

However, Lauren Stevenson is relishing every moment: “I enjoy it, it’s fun,” she says calmly. “The house is always busy, and there are toys everywhere.” Since their return home from the hospital, big brother Axel has been helping his mother with feeding and bathing young Henry. On the other hand, “our middle child Tommie doesn’t quite know what to think of Henry yet,” Stevenson admits, “but we’re all trying to take care of him and have fun with him and enjoy it.”

Like middle baby Tommie Lee, Henry was a speedy delivery, born in under 9 hours: “Originally we had expected Henry to come out on September 4, but then the morning of the 1st it was like, ‘I’m going into labor, let’s go to the hospital,’” Stevenson says. “And it didn’t hit my husband and I until we were at the hospital that, oh my goodness, Henry is going to be born on the 1st like our other two.”

The Stevenson Family

The Stevenson Family

Read more about Henry’s unique birth and birthday on TODAY.