The couple, who found fame on MTV reality show The Hills, tied-the-knot in 2009 but Spencer only dropped the bombshell about babies last year.
Thankfully for Heidi, who is desperate to start a family, Spencer has since changed his mind and promised that she will be pregnant - all being well - within the next year.
In an interview with American magazine Life & Style, Heidi revealed: "Last year, while we filmed an E! special, he told me, 'I don't want to have kids,' and I started crying.
"I told him I couldn't bear the thought of never becoming a mum. So when he saw how important it was to me, he had a change of heart."
Heidi, who celebrated her 28th birthday in September, added: "Spencer promised me a baby by 29."
Two weeks ago, Heidi gave her biggest indication yet that she and Spencer were ready to start trying for a baby after posting a snap of Clearblue ovulation tests on Instagram.
Alongside the photo, she thanked a friend for suggesting she tried them and added: "Shhhh don't tell @spencerpratt lol!"
The tests tell a woman the most fertile times of her monthly cycle, helping to increase the chances of conception.
Prior to this, Heidi had told her Twitter fans about her desire to fall pregnant by posting: "I'm going to write the book, What to Expect When You're Not Expecting... Lol."
Heidi added: "Ok... So I'm a little or a lot baby crazy... Haha." The US reality star, who famously underwent 10 cosmetic procedures in one day in November 2009, has also been posting pictures of her dream nursery on Pinterest.
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