"This news has been difficult to get our arms around. Like every parent, we have hopes and dreams for our children," McMorris Rodgers said in a letter to constituents and supporters. "Although initially stunned, we are embracing our son and preparing for what may lay ahead."
McMorris Rodgers, a second-term Republican from eastern Washington state, was the first member of Congress in more than a decade to give birth while in office.
Down syndrome occurs when a person has three, rather than two, copies of the 21st chromosome. Characteristics associated with Down syndrome include low muscle tone, small stature, an upward slant to the eyes and cognitive delays.
The incidence of Down syndrome increases with the age of the mother. But due to higher fertility rates in younger women, 80 percent of children with Down syndrome are born to women under 35, according to the National Down Syndrome Society.
Jill Strait, a spokeswoman for McMorris Rodgers, said a blood test conducted during the pregnancy indicated an increased risk of Down syndrome because of the congresswoman's age, 37 when she gave birth to Cole, her first child.
The couple "decided not to pursue further testing," Strait said.
McMorris Rodgers said, "Thankfully, Cole appears to be in excellent physical health. We will monitor him closely as he develops, and like all parents, we will strive to ensure Cole has every opportunity to reach his full potential."
She wrote the letter to update friends and supporters following news that her son was recovering after intestinal surgery. The baby, born prematurely April 29, was hospitalized at Bethesda Naval Hospital in suburban Maryland for nearly three weeks.
Since he came home, Cole has been "eating, sleeping and doing his business like every newborn." McMorris Rodgers said. "We are thrilled to be new parents."
The former Cathy McMorris married Brian Rodgers last year.