Skylar Richardson, 20, is on trial accused of murdering her baby and burying her in the backyard in May 2017, when she was 18.
The court was shown photos of Skylar at her prom just two days before she gave birth.
She says she gave birth in the middle of the night on the toilet while her parents were asleep. She claims the baby girl, who she named Annabelle, was stillborn and she buried her in the backyard.
However, prosectors claim she killed the baby by smashing its skull with a rock then set fire to the corpse in a bid to keep it a secret.
The defense showed several photos of Skylar before, during and after her pregnancy.
Despite being heavily pregnant at her prom on May 5, no one realised she was pregnant as her weight fluctuated so much.
Skylar herself knew she was pregnant that night as a doctor had confirmed it on April 26.
She was arrested in July when she went back to the same doctor's practice where her pregnancy was diagnosed to ask for birth control.
In a text to her boyfriend Brandon Saylor just hours after giving birth, Skylar said she'd had a bad night: 'I'll tell you about it later but last night was like the worst ever and I didn't go to sleep till 5.30 but I feel sooooo much better this morning I'm happy.'
Brandon wasn't the baby's father, it was Trey Johnson, another teenager who she'd had a fling with.
Trey told police that he and Skylar 'did stuff' for around a week in July and August in 2016 but that she suddenly blocked him on social media.
The jury heard that Skylar's weight fluctuated due to an eating disorder, making it difficult for people to tel she was pregnant.
'We were in shock. We didn't know she was pregnant,' said her dad Scott Richardson during his testimony, adding, 'We would have taken [the baby] into the family. I think we would have been in shock and we probably would have been angry but...'
An expert witness said that Skylar may have had a intrauterine growth restriction, a common cause for stillbirth.
He said her eating disorder, malnutrition and not taking any prenatal vitamins may have contributed to the chances of this happening.
Prosecutors claim Skylar went to the gym just hours after giving birth and took a selfie which showed off her stomach.
The trial continues.