Tokyo 2020 organisers say “nursing children” can accompany Olympic athletes to Tokyo “when necessary”.
It comes after Canadian basketball star Kim Gaucher, who has a three-month-old daughter, said she was being forced to choose between “being a breastfeeding mum or an Olympic athlete”.
Organisers have banned athletes’ families attending the Games due to Covid-19 safety protocols.
USA footballer Alex Morgan says she is still unsure over the new guidance.
Olympic gold medallist Morgan, who has a one-year-old daughter, tweeted: “Still not sure what ‘when necessary’ even means.
“We are Olympic mothers telling you, it is necessary. I have not been contacted about being able to bring my daughter with me to Japan and we leave in seven days.”
USA captain Megan Rapinoe backed her teammate, saying: “If a mother/father/parent says it’s necessary, it’s necessary.”
When asked for clarity around the issue on Thursday, Tokyo 2020 organisers told BBC Sport: “Children must be within nursing age.
“NOCs [National Olympic Committees] will be responsible for confirming to Tokyo 2020 that children who accompany athletes to Japan require nursing care.”
Gaucher will now be able to bring her daughter with her to Tokyo, and said she was “so relieved I don’t have to make this decision”.
Team GB archer Naomi Folkard welcomed the decision but said it had come too late for her to change her plans.
Her five-month-old daughter Emily will remain in the UK while she is competing in Japan.
Folkard will leave enough frozen breastmilk to last for the two weeks she is away.
“It’s really good that they finally realised that it’s a problem,” she said.
“For me personally it’s not quite enough and it’s too late. I have already made plans and to change those plans would be quite stressful. I would have to work out when to breastfeed, when to express, and how to keep what I had expressed at the right temperature. It’s too much to take on.”