"A minor child deserves privacy and should be kept out of politics," Xinhua news agency quoted Melania Trump as saying in a tweet on Wednesday.
"Pamela Karlan, you should be ashamed of your very angry and obviously biased public pandering, and using a child to do it."
Karlan, a law professor from Stanford University who was called by the House Judiciary Committee Democrats for the panel's first hearing on Wednesday, mentioned the Donald and Melania Trump's 13-year-old son to demonstrate that the President's rights were under the Constitution.
"Contrary to what President Trump has said, Article II does not give him the power to do anything he wants, and I'll just give you one example that shows you the difference between him and a king, which is the Constitution says there can be no titles of nobility, so while the president can name his son Barron, he can't make him a baron," Karlan said.
The President retweeted his wife's message to his 67 million followers.
Karlan later apologized for using Barron's name.
"I want to apologize for what I said earlier about the president's son. It was wrong of me to do that," Karlan told the House Judiciary panel.
"I wish the President would apologize, obviously, for the things that he's done that's wrong, but I do regret having said that."
Karlan was one of three scholars called by the Democrats who testified on Wednesday that they believed Trump committed impeachable offences.
The sole Republican witness, Jonathan Turley, a law professor from the George Washington University, cautioned the House against moving forward with impeaching Trump.
The hearing, marked by partisan disagreements over Trump's conduct toward Ukraine, was the start of the House Judiciary Committee's process of considering potential articles of impeachment against the president.
A House Intelligence Committee report issued on Tuesday accused Trump of soliciting interference from Ukraine in the 2020 election and placing "his personal political interests above the national interests of the US",
Trump has consistently denied any wrongdoing ande White House has so far refused to cooperate with the impeachment proceeding.
( With inputs from IANS )