Tucker Carlson, one of the most popular hosts on the network, made the remark on his Tuesday programme.
Other top brass, as well as veterans’ groups, have also rebuked Mr Carlson.
What did Tucker Carlson say?
Mr Carlson, who hosts the conservative network’s highest rated programme, used part of his show to deride military “maternity flight suits” and recent updates to Army and Air Force hair regulations.
“Pregnant women are going to fight our wars,” he said. “It’s a mockery of the US military.”
“While China’s military becomes more masculine as it’s assembled the world’s largest navy, our military, as Joe Biden says, needs to become more feminine,” Mr Carlson opined.
How did the military respond?
Senior members of the military denounced Carlson’s comments on Twitter.
General Paul Funk, who leads the Army Training and Doctrine Command tweeted that “thousands of women serve honourably every day around the globe”.
“They are beacons of freedom and they prove Carlson wrong through determination and dedication,” he wrote. “We are fortunate they serve with us.”
Major General Patrick Donahoe posted a video of him “conducting a re-enlistment for one of the tens of thousands of women who serve in our Army.”
“Just a reminder that @TuckerCarlson couldn’t be more wrong,” he said.
Mr Kirby said he hoped the commentator would “realise the mistake he made and express some regret about the manner in which he essentially demeaned the entire U.S. military and how we defend and how we serve this country.”
The Pentagon would not take military advice from Mr Carlson in any case, he said.