Amy Crowhurst, who is expecting a baby boy in spring 2003, made her decision after seeing his image during a hospital scan.
Amy could have had an operation to get rid of the unborn baby.
But she said: "When I saw the baby on the screen, I thought, 'No, it's too far gone', so me and my mum decided to keep it."
Amy, of Crawley in West Sussex, fell pregnant five-and-a-half months ago. The father is a boy she met at a youth club.
The baby will be brought up alongside Amy's five-month-old brother, Momodou.
Amy added: "I look after my brother sometimes, so my mum will be helping me with mine."
Mum's anger
Her mother Rose admits she was angry at first. She said: "I was just screaming and shouting at her."
She added: "Basically half of Amy's childhood has just gone. So where she would have been going out to local discos at 16 - she's now got to think of her baby."
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