How Jessica Biel's "serene and natural" birth plan ended with an emergency c-section.

Celebrity couple Justin Timberlake and Jessica Biel had the birth of their first baby all figured out.

They had a doula and two midwives ready to go. They’d done meditation birthing class and read “a ton of hippie baby books”.

They’d even converted their Hollywood Hills home into a labour training facility – nicknamed The Octagon – and were ready to welcome their son into the world in a “serene” and “natural” environment.

Of course, as any parent would know, their carefully thought-out birth plan went out the window when baby Silas decided to make his debut.

Clearly Lil Woody is the boss of this Halloween rodeo! Love, Buzz, Jessie and Woody #HappyHalloween

A post shared by Jessica Biel (@jessicabiel) on Oct 31, 2017 at 4:08pm PDT

The couple – who married in October 2012 before welcoming their first child in 2015 – have shared their birth story in a new book written by ‘nanny to the stars’ Connie Simpson.

In an excerpt from the book – The Nanny Connie Way: Secrets to Mastering the First Four Months of Parenthood – released to ET, the couple credit the celebrity nanny for helping them deal with the first few months with a new baby.

LISTEN: We ask Midwife Cath if a fear of vaginal birth is a good enough reason to have a caesarean. Post continues after audio.

“Our story with Nanny Connie started the day we brought our son home from the hospital. That may sound like a normal statement coming from new parents, except our birth plan was anything but normal,” the pair wrote in the book.

“All our plans fell apart and the serene, natural childbirth we had envisioned ended with a transfer to the hospital and an emergency C-section.

“We arrived home exhausted, disillusioned, and totally in shock.”

The 36-year-old actress said she became a "dictator" after Silas' birth - who "came into this world in an operating room through an incision" - and became obsessed with "everything organic, toxin-free, natural, and homeopathic".

Luckily, Nanny Connie - whose also worked with celebrity parents Emily Blunt and John Krasinski - was on hand to help, and now Silas is a happy, healthy boy who will celebrate his third birthday next week.