"I have felt the pain of her swollen feet and the ridiculous assertions that she would be a lesser performing Prime Minister as a pregnant woman and then new parent. She has skedaddled that myth."
Chadwick said Ardern was an inspiration for other working mums.
With her midwife hat on, she said she hoped Ardern would "just go with her body now and enjoy the birth, trust her professional advice and let Clarke be her assertive partner as they both navigate a very unique experience together".
"I used to tell new mothers to let those hormones wash over them and focus on attaching to that new person to allow rhythms to develop.
"Just remember, they don't differentiate between day and night so grab sleep whenever the opportunity arises. As a politician she has learned to manage on snatches of sleep anyway."
When she ran her first campaign in politics Chadwick's slogan was "From labour to Labour".
"Now it's the reverse for Jacinda.
"Mum and Dad, whānau and Koro Winston will manage the business, and the Labour Women's Caucus will act as Aunties. Kia kaha from Rotorua."