"I remember one time I just had a miscarriage and Rachel was giving birth.
"Oh my God, it was terrible having to be funny."
She has gone on to speak openly about her experiences, sharing that: "I had a lot of miscarriages and I don't think that's something people shouldn't talk about because it's β¦ unfortunate, but it happens.
"I just think it's important to get things out there so people can realise they're not alone."
Following two rounds of IVF, Cox gave birth to her daughter Coco in 2004 - the same year Friends wrapped.
Cox and Coco's father, Arquette, divorced in 2013.
Now 15, Coco is a regular feature on her mother's Instagram account and the pair share a close bond.
"Coco has taught me so much," says Cox.
"I try to make Coco feel strong and confident by listening to her, listening to her feelings β¦ She is incredible.
"Sometimes I do wish her shorts were longer," she said. "But I want to keep an open relationship with her."
The teen also counts her mum's best mate, Jennifer Aniston, as her godmother.
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β’ Friends reunion confirmed: Jennifer Aniston, Courteney Cox and co to team up for new special
β’ Friends star Courtney Cox 'so excited' for HBO reunion special
β’ One-off Friends reunion could be a 12-part series worth $1 billion
β’ Friends reunion deal reportedly close to completion
