Richie told TMZ that a social worker gave him the extremely upsetting news that the couple lost a "beautiful boy." Richie revealed he was given the opportunity to hold his son and that he picked the name Rex Jagger Lamas-Richie.
Richie explained that he "always wanted a son named Rex" and Jagger is after musician Mick Jagger.
The heartbroken father also penned a letter to his late son "R.J," which he shared with the site.
"I'm writing this to say thank you, to let you know how truly blessed I am to be your father," Richie wrote. "You brought meaning to your parent's life in a way you'll never know and you'll always be in our hearts and thoughts."
He continued, "God has a plan for us all. He gave me an amazing son who will always watch over our family. You saved your mother's life with your passing and I will never forget how much this means to me, R.J. In family, we sacrifice for each other. You gave your life for us. You showed me how to love."
"I need you to know that I held you, spoke to you, kissed you and that you'll be remembered," he concluded. "You are perfect. You will always be my son. I'm proud of you, always. I love you, Rex Jagger Lamas-Richie.
Lamas was rushed to the hospital on Feb. 9 after Richie discovered that she had collapsed inside the family's Orange County home.
TMZ reported that upon arriving at the local hospital, doctors found that Lamas was "bleeding internally around her uterus and the situation was dire."
During emergency surgery on the 28-year-old, Lamas lost her baby. It was announced just last month that she was pregnant with her second child and was entering her second trimester.
On Monday, Richie posted on his blog that Lamas is still in the intensive care unit.