Christensen's mother was an unwed teenager who gave birth to him when she was 15 -- an age where many teens have an abortion because their pregnancy is frequently a result of sexual assault.
"I also can't help but look back and think of how easily my life and thus generations to follow could have been snuffed out before it ever got started," Christensen shared last year at a site for adopted people.
"I can't help but think of a 15-year-old, unwed, pregnant teen who made a courageous decision not to abort her child, but instead gave him a chance at life that over 50 million children since have not had. That child was me," he said.
Christensen was adopted, with his mother leaving specific instructions at the Los Angeles County Hospital to place her child in a Christian home or saying she would take Christensen back.
He has still never met his birth mother -- "but I am so grateful for her courage to have her child when it wasn't and still isn't to this day the choice of most."
"I am grateful for her unselfishness in wanting the best life for me and the decision that I might benefit from life in another family. I'm touched by her faith in entrusting her child to God with confidence," the Colts coach says. "She trusted God would find the right family and would watch over her child throughout his life."
Christensen and his wife Debbie are so concerned about the unborn children who are killed in abortions that they are very involved in Life Centers, the network of pregnancy centers in the Indianapolis area.
Debbie has been a regular peer counselor at the West Pregnancy Center.
Brian Boone, the president of Life Centers, recently shared Christensen's story via email with supporters of the organization. He said Christensen recently met with a client named Tiffany who decided to give birth to her son with the center's help.
"[He] recently met Tiffany and shared that he has a similar story. Over 50 years ago, his teenage mother chose life for him and placed him for adoption in a Christian household," Boone writes.
"He told us that decisions for life, like Tiffany's choice, affect generations. As he watches his daughters making an impact on our world for Christ, he sees how one difficult, but right choice can impact humanity for decades and bring about spiritual victories - which are bigger than those we see on the football field," Boone said of Christensen.
And Debbie "meets with women who are facing the choices between life and death. In her kind, nonjudgmental manner, she offers a servant's heart and encouragement to women like Tiffany when they need her most," Boone explains.
Ultimately for Christensen, he credits his adoption with giving him a fullness of life he now enjoys.
"I am a husband, a father of three terrific daughters, and I'm an NFL football coach. I don't know of anyone whose life has been more blessed than mine," he says. "Coaching has given me the opportunity to influence many young lives throughout the years. And today, my own beautiful girls have and will continue to impact this world for good. What an impact one right decision can have."