The Central Criminal Court has heard Laois nanny Aoife Phelan was not pregnant at the time of her death.
The State Pathologist Professor Marie Cassidy has told a jury that the 30-year-old died from ligature strangulation.
Robert Corbet of Sheffield Cross, Portlaoise, admits killing Aoife Phelan in 2012 but denies her murder.
Her body was found in a barrel buried in a field.
In garda statements, the accused said Aoife Phelan had told him she was pregnant and that he killed her because she was threatening to make his life hell if he walked away from her.