She gave birth in the ambulance on the way to Södersjukhuset in Stockholm on Tuesday evening.
"It was traumatic and magical, all at the same time", writes Sjöström.
"He was born right there, in the chaos outside the hospital entrance in the ambulance. The moment that changed everything: when he was placed on my chest and we heard his first cry".
Swimming star writes that she and her husband Johan de Jong Skierus had been in for a check-up five hours before the son was born, but the couple was sent home. Everything changed quickly when they got home again.
"Started bleeding"
"I started bleeding and we immediately called the delivery ward at the hospital where we were going to give birth. The midwife probably understood through how I was breathing that I was already in labor and insisted, thank goodness, on sending an ambulance", writes the 32-year-old.
"The journey to the hospital felt endless even though it went at full speed with sirens. The pain was indescribable and it was too late for any pain relief that I had planned to take. I really didn't think I would survive", she writes.
Son Adrian was born at 20.05 on August 26.
"From indescribable pain and fear to the most magical moment in our lives".
Sarah Sjöström has previously announced that her swimming career will continue after parental leave.
She has her sights set on the Olympic Games in Los Angeles 2028 - it would be her sixth Olympic Games since her debut in Beijing 2008.
The 32-year-old has taken the most individual World Championship medals in long course of all time - 23 (14 gold) - and six Olympic Games medals (three gold).
Nearly 100 medals
Sjöström broke through as a 14-year-old when she took European Championship gold in the 100 meter butterfly, and since then the Swede has not been able to stop reaping successes. In total, Sjöström is soon up to almost incredible 100 medals from the Olympic Games, World Championship and European Championship.
Now a new life begins when she will combine the mother role with getting back to the world top.
Focus after pregnancy will be to find a strong, stable body again and a training load that makes me able to stay injury-free for many years to come. I will have different physical conditions when I have given birth and will probably never be at the same load again as before the Olympic Games in Paris, Sarah Sjöström has told TT.
Born: August 17, 1993 in Rönninge, Stockholm County.
Club: Södertörns simsällskap.
Coach: Antonio Lutula.
Olympic Games merits: Gold: 100 meter butterfly in Rio 2016, 100 meter freestyle in Paris 2024, 50 meter freestyle in Paris 2024. Silver: 200 meter freestyle 2016, 50 meter freestyle 2021 in Tokyo. Bronze: 100 meter freestyle 2016 in Rio.
World Championship merits (long course): 14 gold, 8 silver, 3 bronze.
European Championship merits (long course): 17 gold, 7 silver, 4 bronze.
Medals in total: Has 97 medals in total in long and short course between 2008 and 2024.
Other: Has been awarded the Jerring Prize twice (2014, 2015) and the Bragdguldet twice (2015, 2017).
