Writing candidly about her personal experience with motherhood, the woman said she used to be a "vibrant, interesting, fun person with a great family life and hobbies, purpose and fulfilment" but now is "a shell of [her] former self".
"My world is so, so small," she wrote.
"If I could hit a button and go back to a time before my son existed, without remembering him or knowing he existed, I would do it without hesitation.
"I regret having a baby so much and I wish with all my heart and soul I hadn't done it."
Parents on the forum had words of advice and encouragement for the woman, with many telling her that, while the first few years are hard, things do get easier.
When forum users asked her if maybe she doesn't have enough support around her, she explained her partner is "amazing" and does "way more than his fair share".
"But I can see what a burden I am to him by feeling this way and I am so so worried about the toll it takes on him, having to be a parent and also support me through this," she wrote.
Many parents on the forum shared their own experience with the new mum and said they felt for her.
"I'm really sorry for you. There is a huge pressure on new mums to be over the moon despite the first year being very hard for many, many women," one parent wrote.
"Oh poor you. It sounds like you are feeling terrible at the moment. I just wanted to say that it doesn't sound unfamiliar," another person said. "I love being a parent, my daughter is [a toddler] and I went through hell and back to get her here but I have definitely had lots of moments where similar thoughts have gone through my mind.
"I really didn't enjoy the newborn stage at all. I just wanted to say, I do feel it gets better the older they get."
Many of those who commented advised the woman to seek counselling as she could be suffering from postnatal depression.
Others pointed out that the hardships of new parenthood are often underestimated.
"Just for the record, you don't need to have PND to feel this way. Having children can wreck your mental heath, your body that you will never get back, your finances and freedom. Women need to be educated about the reality and not be influenced so heavily on social media. I feel for you," one person wrote.
In the comments, the new mum has since written that she is seeking professional help.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
