The Law & Order: SVU star had finalised an adoption plan with a woman who wanted to give up her unborn child, and was even in the delivery room when the tot came into the world.
Hargitay and her husband Peter Hermann parented the newborn for two days - only to be told the biological mum wanted the baby back.
She tells Good Housekeeping magazine, ""It was nothing short of devastating. But... it was probably the greatest, happiest ending. I mean, it was so painful for us, but it was deeply joyful and deeply right for her.""
Hargitay went on to adopt son Andrew and a daughter, Amaya, in the space of six months last year (11) - and she admits the process has been challenging.
She adds, ""I'm not gonna lie, there were wrenching moments. I say to everybody, 'Adoption is not for the faint of heart.' Adoption was a bumpy ride - very bumpy. But, God, was it worth the fight.""
Hargitay and Hermann are also parents to a five-year-old old biological son, August.