The co-host of the "Mom Brain" podcast revealed the exciting news in an Instagram video on Wednesday, sharing her baby's heartbeat from an ultrasound with her followers.
"It is still very early...but we have learned that there is a little person inside of me," Hilaria, 35, wrote. "The sound of this strong heart makes me so happy—especially because of the loss we experienced in the spring. We want to share this news as we are excited and don’t want to hide the pregnancy.
"These first few months are tough with exhaustion and nausea...and I don’t want to have to pretend that I feel ok," she added.
Hilaria also requested that paparazzi leave her be, stating that, "I want to remain peaceful during this very early time in my pregnancy and getting chased around by cameras is not in the doctor’s orders."
The fitness guru also posted a mirror selfie the same day, showing off her baby bump.
"When you’ve had so many babies, 6 minutes pregnant = looking like 6 months pregnant," she joked.
Alec revealed the couple's desire to have another baby earlier this month in an appearance on Kevin Nealon's YouTube series, "Hiking with Kevin,"
"We have four kids. She wants to have another one. We’re having another one," he said. "We're gonna have a fifth baby."
However, when Nealon asked if Hilaria was pregnant, Alec said: "No. No, no, no — not that I know of," he clarified.
In April, Hilaria revealed on social media that she had suffered a miscarriage.
"There was no heartbeat today at my scan...so it’s over...but I have some pretty strong and amazing heartbeats right here," she captioned an Instagram photo of herself alongside Alec and their four children.
The baby will join big sisters Carmen Gabriela, 6, and big brothers Rafael Thomas, 4, Leonardo Ángel Charles, 3, and Romeo Alejandro David, 16 months.
Fox News' Julius Young contributed to this report.