Motivated by the birth of Sen. Tammy Duckworth’s daughter last week, on Wednesday night the Senate passed by unanimous consent a rule change allowing lawmakers to bring infants onto the Senate floor. It is the first Senate rule change since the 1970s.

Sen. Duckworth, who submitted the resolution, had said she was worried that the rule that barred senators from voting by proxy could make it difficult as the mother of an infant to participate in votes, which can sometimes last hours, particularly while breastfeeding. Rules related to conflicts of interest do not allow her to hand the infant off to people on her staff.

“These late-night votes happen more than people think,” Sen. Amy Klobuchar said Wednesday. “And if you don’t have a baby sitter, it can be hard. If you want people with normal lives, they need to be able to bring their infants.”

Klobuchar, the ranking Democrat in the Rules Committee, and Sen. Roy Blunt, the committee chairman, supported the rule change early on. “It’s an example of changing workplaces and trying to make things more family-friendly,” Klobuchar said.

There are now a record 23 women serving in the senate. Duckworth was the first ever sitting senator to give birth.