The grim discovery was made by her father and a plumber who had been called out after her parents had problems with their drains for two years.
The court heard how the baby - named William - was found in a "seriously decomposed" state and with a fractured skull - but a cause of death was not ascertained.
Connett, from Hertford, was due to be sentenced at Grimsby Crown Court after admitting trying to conceal the birth of a child by secretly disposing of his body between August 6 and August 13, 2013.
But the hearing was dramatically halted yesterday after the court heard she had "repeatedly lied" about what had happened, reports Grimsby Telegraph.
Judge Jeremy Richardson QC told the court that he was concerned about the basis of the psychiatric report, which seemed to be centred around her version of events.
He said the court "has reservations about this ... because she has lied".
He added: "This is a woman who has repeatedly lied to her parents, lied to the police repeatedly and there are countless lies in this case.
"It worries me that the psychiatrist has set so much store by something that may not have actually occurred."
The baby's body is believed to have been placed in the drain between August 2, 2013, and August 13, 2013, at the bottom of the garden of Ann and Stuart Connett, in Scartho Road, Grimsby.
The body wasn't discovered until February 11, 2016.
Prosecutor Jeremy Evans said that Connett was now known as Sinead Layfield after marrying in November.
"She will be using her married name now," said Mr Evans.
The couple now live in the Hertford area.
Judge Richardson said of the psychiatric report: "None of this sits comfortably with me. I just was so concerned."
Connett had told a "catalogue of lies".
The psychiatrist could not be contacted and the case was adjourned for a court-ordered additional psychiatric report to be prepared.
Judge Richardson added: "She has lied to goodness knows how many people."
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