image source, Getty Imagesimage captionMs Holmes has pleaded not guilty to 12 counts of fraud

The first patient to take the stand in the trial of Theranos founder Elizabeth Holmes said the company's blood test inaccurately said she had miscarried.

Brittany Gould, 31, told jurors she had already miscarried three times when she took a Theranos test at a Walgreens drug store after becoming pregnant.

Ms Gould became emotional on the stand recalling the moment she was told. She eventually had a healthy baby.

Ms Holmes has pleaded not guilty to a dozen fraud charges.

Prosecutors have argued she deceived investors and patients by claiming Theranos could detect common illnesses using just a few drops of blood from a finger prick.

Her lawyers have said she was merely a naive businesswoman whose firm failed.

Ms Gould is the first of 11 patients to be called by the prosecution in the case against Ms Holmes.

On Tuesday, the Arizona medical assistant testified she had seen a presentation at her own clinic by a Theranos representative and was impressed by the low price.

She then chose Theranos for a HCG hormone test late in 2014 after an initial test with Quest Diagnostics indicated she was pregnant.

Nurse practitioner Audra Zachman also took the stand and recounted giving Ms Gould the Theranos results.

There was "no medical explanation" for Ms Gould's hormones to have changed so dramatically between the first and second test, Ms Zachman said. "I felt very uncertain of the validity of the results."

Two subsequent tests with Quest confirmed Ms Gould's pregnancy. She later gave birth to a healthy baby girl.

Ms Zachman complained to Theranos about the test. The company responded blaming a human data-entry error.

Ms Holmes' defence team successfully blocked testimony from Ms Gould about the emotional effects of the inaccurate test, so such testimony did not emerge from trial.

But in an interview with the Wall Street Journal last month, Ms Gould described "emotional turmoil" and the dread of telling her then seven-year-old daughter, who was waiting for a younger sibling.

"Mommy is not having a baby," Ms Gould said she told her.

The closely-watched case against Ms Holmes is expected to take months, with more than 140 potential witnesses called by the defence and prosecution.