The Malcolm in the Middle actor, 34, and his wife Paige Price announced their baby news on Saturday with a video on their YouTube channel.
"In the past four-and-a-half years, Paige and I have experienced so many incredible things together. We've traveled the world, got to live out all these once-in-a-lifetime opportunities. While we still believe it's the little moments in between the big ones that make you feel happiest, nothing quite compares to hearing your little one's heartbeat," Muniz said.
"We felt like we were living and experiencing a real-life miracle for the first time. The second I heard that heartbeat, reality set in. I was throwing out baby names and future career choices," he shared.
The couple wed on Feb. 21, months after eloping in October 2019. "We definitely want to have kids!" they told PEOPLE after their magical ceremony earlier this year.
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In the video, the mom-to-be also spoke about the "struggle" to get pregnant.
"When we found out we were expecting, I think we were both in a state of disbelief. We knew that we wanted this, but we were told our chances weren't that great. The struggle of going to every doctor's appointment made me feel less and less like a woman," she said.
"I'm excited to say we beat the odds and we're officially 15 weeks along and counting," Price happily announced.
"We're both really excited for the future and we can't wait to meet our little one," Muniz concluded.
"We were shocked and thrilled to hear the news that we’re going to be parents. We're currently traveling through Jackson, Wyoming and we decided to make a little video!" the parents-to-be captioned their video.