"I think it is imperative we do do something to help young mothers."
He said MPs with young babies could already miss select committee meetings outside of Wellington without requiring a replacement or affecting the vote on the committee.
Ms Mahuta said putting rules in place that made nursing a child easier would help attract young women into Parliament.
Green MP Holly Walker is expecting a child in September and said a change to the leave rules would make a difference.
"The hours are one of the biggest hurdles to having young children in Parliament, especially if you're breastfeeding. But if it was unavoidable, such as where care arrangements fell through and you were on House duty, I'd like to know I could do so without it making a scene."
Labour whip Chris Hipkins said the party would support a change to give nursing mothers leave on top of the usual allocation.
Every effort had been made to give Ms Mahuta as much leave as possible, but sometimes that was impossible because other MPs also had commitments outside Parliament.
Current rule
* Parties must have 75 per cent of MPs in Parliament to cast all votes, regardless of the reasons for individual MPs being on leave.
Proposal
* Allow nursing mothers special leave on a case-by-case basis, such as urgency or late nights, on top of their party's usual leave quotas.