Vanessa Lachey Details Son Phoenix's 'Traumatic' Hospital Experience as Newborn

Vanessa Lachey took to social media to open up about her and husband Nick Lachey's son's Respiratory Syncytial Virus (RSV) diagnosis that left him hospitalized after his premature birth.

The actress shared a photo of Phoenix, who is almost 2, when he was a baby and wrote about what it was like to care for her son who was born 10 weeks early. In the photo, Phoenix, who is wearing a hospital gown and wrapped in a blanket, has a breathing tube up his nose.

"When I gave birth to my youngest, Phoenix, at 30 weeks, I knew he would need extra care," she began. "But I wasn't aware that he was at an increased risk for a common respiratory virus called #RSV due to his under-developed lungs and immature immune system."

She went on to reveal that he spent six days in the hospital "for severe RSV disease."

"I was shocked and terrified. I wish I had known more about RSV before this traumatic experience," she wrote.

She said she partnered with AstraZeneca, a pharmaceutical company, to promote awareness about RSV during RSV Awareness Month.

Those with RSV typically experience cold-like symptoms like coughing, runny nose and fever. Most RSV infections clear up on their own within two weeks, but it's especially dangerous for infants as it can cause breathing difficulty and dehydration, according to the Center for Disease Control and Prevention.

The mom of three encouraged her followers to talk to their baby's doctor about RSV prevention.

Nick and Vanessa Lachey, who also share Brookyln Elisabeth, 3, and Camden John, 6 discussed Phoenix's scary entrance into the world when they both competed on Dancing With The Stars last year.

"I'll never forget. She called me in a panic: 'They're taking me in for an emergency surgery. Get here as quick as you can,'" Nick recalled on the show's "Most Memorable Year" episode. "I think as a man, you want to believe you can protect your kids, protect your wife. I felt so helpless."

Vanessa vividly remembers the moments surrounding her emergency C-section: "I was on the operating bed and I looked up and I didn't know a single face and I remembered thinking 'I hope the baby's okay and don't worry about me. Just make him okay.'"

Nearly two years after Phoenix was born, the parents can celebrate how far he's come. In January at a Pampers event, the parents opened up about their son's health struggles before, saying that they had to adjust their expectations when it came to Phoenix hitting milestones.

"What I've had to do for myself now as a mom of a preemie is not to count the milestones," Vanessa said in January. "I mean that loosely and with love — to not compare him because every kid is going to be different, especially a preemie."

The parents said they are careful not to compare what Phoenix is doing to what Brooklyn and Camden were capable of at his age.

"He's smaller, but he's healthy. He's so happy," Vanessa said. "Brooklyn and Camden were standing and walking a little bit at this point and he's not even near that. And I'm okay with that because every kid has their own time and their own moment and instead of us dwelling on what he's not doing, we're just living and relishing in what he is doing."

"He's the happiest, most joyful kid ever," Nick added. "He's crawling everywhere, he's so curious and into everything now."