The 23-year-old Olympian - who is expecting a son with husband Dustin Lance Black via a surrogate - has always wanted to have a child and admits it was "hard" knowing he may never become a father, but he has made sure he is prepared by splashing out on numerous garments for his little one over the years.
He said: "It's great having a husband, it's quite a romantic marriage. I always wanted to get married and have children even before I met Lance.
"I've been buying baby clothes for the last six years, it was something that really mattered to me.
"Knowing it meant I might not be able to have a kid was hard. If you are in a straight relationship it can just be a matter of a glass of wine and a pizza on the sofa. To want a child as a same-sex couple is a tough process, a long process."
Tom and Lance are unsure which of them is the biological father to their unborn child - who is due in June - and while they have a great relationship with their "amazing" surrogate, the diving sensation has been "terrified" reading numerous baby books ahead of the birth.
He said: "We found an egg donor and we are the sperm donors, we have fertilised half the eggs each. We put in a boy embryo and a girl embryo and we don't know whose is whose. The next time we will do it the other way around.
"Ours [surrogate] is the most amazing woman, she is lovely and kind and generous. The baby books are terrifying.
"I've read up far too much, but we are both going to take time away from the pool and work."
While Tom is unsure who his and Lance's baby will take after, he is already planning to set the youngster on a path to follow in his diving career footsteps by putting him in water when he turns three months old.
He added to The Times newspaper: "All our family and friends are, like, 'Are you going to get him into sport or film?' But you never know what a child is going to be like. We've never met the egg donor so we don't know about her.
"All we can do is love the living hell out of him and support whatever he tries ... but I suspect he'll be in a pool by three months."