Vargas and her husband, singer-songwriter Marc Cohn, are expecting their second child in late summer, they announced Friday. The couple have a son, Zachary, 3, and Cohn has two children — Max, 14, and Emily, 11 — from a previous marriage.
Vargas, who with John Stossel also co-anchors the ABC newsmagazine "20/20," will continue to anchor both programs through late summer.
"I told Elizabeth that during such a difficult time for all of us, it's good to get such wonderful, life-affirming news," ABC News President David Westin said in a statement.
Woodruff is being treated at Bethesda Medical Center in Maryland for injuries he sustained in an Iraqi roadside bombing on Jan. 29.Vargas, 43, and Woodruff, 44, debuted as "World News Tonight" co-anchors Jan. 3.
They succeeded longtime anchor Peter Jennings, who had been off the air since April, when he announced during his broadcast that he was battling lung cancer. He died in August.
In Jennings' absence, both Vargas and Woodruff served as a substitute anchor of "World News Tonight," as did "Good Morning America" host Charles Gibson.
After Woodruff's injury, both Gibson and his "GMA" co-host Diane Sawyer have filled in, and will continue to do so "for the next few weeks," said ABC News spokeswoman Cathie Levine.
"When we have more information about Bob's recovery, we'll put a plan in place to take us forward."
Referring to any maternity leave Vargas might take, Levine added, "We'll factor that in, as well."