Tammy Davis-Charles, 49, was arrested in late November with two Cambodians and accused of recruiting foreign couples and Cambodian surrogate mothers to a clinic in the capital Phnom Penh.
The detentions came just two weeks after Cambodia moved to outlaw the surrogacy industry, which critics say exploits poor women, after a similar ban in neighbouring Thailand pushed the business across its borders.
The trio were also charged with faking documents to obtain birth certificates for the newborns.
In court on Tuesday Davis-Charles said she played no part in arranging surrogacies.
Instead she said her role was limited to providing medical care to a total of 23 surrogate mothers who carried babies for 18 Australian and five American couples.
"They find the clinic" by themselves, she said of the would-be foreign parents, adding that she was also not involved in the recruitment of Cambodian surrogates.
The nurse said she received $8,000 from each couple while surrogates received around $10,000.
All of the infants were born and moved out of Cambodia before her arrest, she added.
Davis-Charles, who is from Melbourne, told the court she left Thailand more than a year ago after Bangkok outlawed commercial surrogacy and moved to Cambodia, which at the time lacked regulations on the industry.
Two surrogate mothers testified in court on Tuesday to receiving $10,000 from Tammy.
Surrogate mother Hor Vanday said she gave birth to a baby girl who was whisked away for a foreign couple.
"I did not see the face of the baby, but I know her father took her away," she recalled. She added that she did not miss the child as she knew it was never hers.
Thailand for years hosted Southeast Asia's most thriving unregulated surrogacy industry that was particularly popular with same-sex couples.
But several scandals in 2014 -- including tussles over custody -- spurred the government to bar foreigners from using Thai surrogates.
Surrogacy consultants say Laos, a poor and opaque communist country to the north, has since emerged as the next frontier for the "rent a womb" business in the wake of the recent bans by Cambodia, Thailand, Nepal and India.
A number of Laos-linked surrogacy agencies and IVF clinics have cropped up in recent months, according to consultancy group Families Through Surrogacy. A Thai man was recently arrested for smuggling frozen sperm between the two countries.
