Beyonce has revealed one of her twins' heartbeats "paused a few times" while she was in labour.
The Formation singer, 37, said she had to have an emergency caesarean to deliver Sir and Rumi Carter, now 22 months old, reports news.com.au.
Speaking about her pregnancy in her new Netflix documentary Homecoming, Beyonce said her "body went through more than I knew it could".
"I was 218 pounds (98kg) the day I gave birth. I had an extremely difficult pregnancy," Beyonce said.
"I had high blood pressure, I developed toxaemia, pre-eclampsia and in the womb, one of my babies' heartbeat paused a few times so I had to get an emergency C-section."
She revealed the pregnancy took a huge toll on her physically and that she had to "rebuild" her body "from cut muscles … what people don't see is the sacrifice".
"My body went through more than I knew it could," Beyonce said, in Homecoming.
"I definitely pushed myself further than I knew I could and I learned a very valuable lesson: I will never never push myself that far again".
Beyonce's highly-anticipated documentary premiered on Netflix yesterday, with the Lemonade singer stunning fans by also releasing a new live album.
Homecoming: A Film by Beyonce documents her record-breaking set at Coachella Valley Music and Arts Festival in 2018 — dubbed "Beychella" — when she became the first black woman ever to headline the Californian music festival.
"It's my first time back home on the stage after giving birth. I'm creating my own homecoming and it's hard," Beyonce said, of the performance.
"There were days that I thought I'd never be the same, I'd never be the same physically, my strength and endurance would never be the same."
Homecoming: The Live Album, features 40 songs from her two-hour set including Formation, Sorry, Drunk in Love and Flawless.
Destiny Child songs Lose My Breath, Say My Name and Soldier also feature, as Beyonce reunited with Kelly Rowland and Michelle Williams on stage.
Her live album is available now on streaming platforms Tidal, Apple Music, Spotify and Google Play.
Of course, Homecoming has caused near-hysteria among Beyonce's fans, the "Bey-hive", on social media.
They've called the doco "unmatched" with #BeyonceHomecoming trending worldwide.
Netflix described Homecoming as "the emotional road from creative concept to cultural movement" — and it features both behind the scenes, and concert and family footage of the first of her two headline sets at Coachella.
Beyonce had originally been booked to headline Coachella in 2017 after the release of her album, Lemonade, but was forced to postpone after announcing she was pregnant.
Less than a year later, she was onstage in the Californian desert to make history with her headline slot on Saturday night, which included the voice of Malcolm X and a version of Lift Every Voice and Sing — a song widely considered to be the black national anthem.
In the lead up to the performance, Beyonce's mother Tina Knowles said that her daughter had told her, "I have worked very hard to get to the point where I have a true voice".
"And at this point in my career, I have a responsibility to do what's best for the world and not what is most popular".