ET has reached out to Kim's rep.
Kim has been very open in the past about wanting to be pregnant again, but being unable to do so because of health risks. The mother of two had notoriously difficult pregnancies with both her 4-year-old daughter, North, and her 1-year-old son, Saint.
"It's something that has been in the works for a bit now," a source close to the couple told ET in June of the surrogacy decision. "There was always a very high risk if Kim became pregnant with a third baby, so it was never really an option. They are excited to finally add to their family."
Our source said Kim and 40-year-old Kanye agreed to pay the surrogate 10 monthly installments of $4,500, totaling $45,000. If there are multiple children, the surrogate will get $5,000 for each additional baby, and if the surrogate loses reproductive organs, she gets $4,000. Kim and Kanye were also required to deposit $68,850 with the agency they used to find their surrogate.