Adams finished inside the top 10 in the field at the 2004 Olympics in Athens, before claiming gold in both Beijing and London. In 2016, she claimed the silver medal in Rio de Janeiro.
She had alluded to attempting to compete in Tokyo last year. In October, after announcing she was pregnant with her second child, she said: "The risk of completing our family and training for the Olympics ... I don't want that. First and foremost for me was actually giving Kimoana a sibling and completing a family. For us this is it.
"I don't want to come end of Tokyo, look back and have any regrets.
"I don't want to be one of those should've, would've, could've. I've got the opportunity now, I need to take it. It's the same with sport, if you've got the opportunity, take it."