"Homecoming" a film by Beyoncé. Picture: Netflix

Beyonce had to have an emergency caesarean section after her baby's heart stopped "a few times" in the womb.

The Formation songstress - who has seven-year-old Blue Ivy and 20-month-old twins Rumi and Sir with her rapper husband Jay-Z - spoke about the "extremely difficult" pregnancy and delivery she had with her youngest children in her newly-released Netflix documentary Homecoming: A Film by Beyonce, revealing she suffered a number of health issues throughout.

Explaining how her "surprise" pregnancy meant she had to scrap her planned headline slot at the 2017 Coachella festival, Beyonce said: "I was supposed to do Coachella the year prior but I got pregnant unexpectedly. And it ended up being twins which was even more of a surprise."

"My body went through more than I knew it could. I was 218 pounds [about 98kg] the day I gave birth. I had an extremely difficult pregnancy. I had high blood pressure. I developed toxemia, preeclampsia.

"And in the womb, one of my babies' hearts paused a few times so I had to get an emergency C-section."

The 37-year-old singer had to "sacrifice" spending time with her children to headline the festival in 2018, and the Crazy in Love hitmaker suffered "muscle spasms" when she first started rehearsing for the two-hour concert because her "body" was no longer "connected" to the stage.

Speaking on her Netflix documentary, she said: "In the beginning there were so many muscle spasms and just internally, my body was not connected. My mind was not there. My mind wanted to be with my children. What people don't see is the sacrifice.

"I would dance and go off to the trailer and breastfeed the babies, the days I could I would bring the children. I'm just trying to figure out how to balance being the mother of a six year old and twins that need me and giving myself creativity. Physically, it was a lot to juggle.

"It's like, before I could rehearse 15 hours straight. I have children, I have a husband, I have to take care of my body."

The Single Ladies singer also explained that having children has made her a "new woman".

She added: "I just feel like I'm just a new woman in a new chapter of my life and I'm not even trying to be who I was. It's so beautiful that children do that to you."