The test results showed a significant drop in pregnancy hormones early in the pregnancy, an event that, if the results were accurate, would be "very concerning," the nurse practitioner, Audra Zachman, testified.
The patient had already miscarried three times.
The results showed a swing over a two-day period from higher-than-normal values in early pregnancy to a level that indicated the body was already starting to eliminate the pregnancy hormones.
Zachman told the patient that it was looking like a miscarriage after getting the mystifying Theranos results.
In fact, the story has a happy ending, as the patient, who also testified on Tuesday, successfully carried a baby girl to term.
But the experience, Zachman said, left her very uncertain as to the validity of the Theranos lab results, adding that continued use of the services made her "uncomfortable as a provider."
Holmes is charged with 12 counts of wire fraud and conspiracy to commit wire fraud, based on allegedly false and misleading statements about Theranos' blood-testing technology. If convicted, Holmes faces up to 20 years in prison and $3 million in fines.
Earlier in the day, Holmes' defense team completed its cross-examination of Surekha Gangakhedkar, a scientist who worked for Theranos for eight years and resigned just before the launch of the company's blood-testing technology in Walgreens, out of concern that it was not safe to use on patients.
Defense attorney Lance Wade brought up a series of blood tests, known as assays, that Gangakhedkar and her team successfully developed in the Theranos R&D lab.
Gangakhedkar acknowledged that she was "proud of that work."
The defense is seeking to establish, as it argued in its opening statement two weeks ago, that although Holmes ultimately failed in developing technology once viewed as visionary, "Failure is not a crime."
Referring to the many problems she and her team had in running the blood tests on the Theranos Edison machines, Gangakhedkar agreed with defense counsel that "sometimes you have to fail before you can succeed."
But Gangakhedkar pushed back on defense efforts to undermine her testimony that Theranos operated a secretive workplace where information was siloed.
Although emails and calendar invitations showed some sharing of information, Gangakhedkar maintained that the interteam emails had only high-level information, not details.
She testified that staff were told several times in meetings not to talk about the assays they were working on.
Three days before her resignation in September 2013, Gangakhedkar received an email from Ramesh "Sunny" Balwani, Holmes' business partner and former lover, telling Gangakhedkar's team to "put in the hours this month to bring up all assays and work around any challenges that come our way."
Gangakhedkar testified that the idea that her team was somehow not pulling its weight was a common theme that was unfair and deeply frustrating.
The court refused to allow defense counsel to ask whether Balwani also pressured Holmes to work harder.