Sarah Louise Catt, 35, took drugs she'd bought on the internet when she was 39 weeks pregnant to cause an early delivery.
Leeds Crown Court was told that Catt's husband – the father of their other two children - was unaware of the pregnancy and was not consulted about her decision to have an abortion.
The judge heard that Catt, from Sherburn-in-Elmet, North Yorkshire, had been having an affair with a work colleague for seven years and that she clearly thought her lover was the father of the aborted child.
She has never revealed what happened to the child except to say it was a boy and that she buried him.
The judge said Catt made a 'deliberate and calculated decision' to end her pregnancy knowing the child could live.
She'd had a scan at 30 weeks confirming her pregnancy at a hospital in Leeds, but suspicions were raised when she failed to register the birth weeks later.
She maintained she had a legitimate abortion at a clinic in Manchester, but analysis of her computer revealed she had purchased a drug called Misoprostol which can induce labour.
Catt pleaded guilty earlier this year to administering a poison with intent to procure a miscarriage.
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