Marina Tilby, 26, was jailed for child neglect after she fell asleep face down on top of her son Darrian, who later died.
She was sentenced to two years and four months.
On March 30 2017, Tilby had been in the Sea Horse Inn in New Quay, Wales, where she had been seen drinking Guinness, Swansea Crown Court heard.
After buying bottles of gin and port with her sister, the court heard, she took a taxi to Quay West holiday park to watch a tribute act at the clubhouse.
The court heard she continued drinking and was seen dancing with her baby, throwing him in the air and catching him. Witnesses also said she was seen breastfeeding.
Tilby and her sister later went back to a caravan with a group of men they had met that night, where they continued drinking before the mother passed out on top of her child, the court heard.
In the early hours of March 31, the sister saw Tilby lying on the child and managed to pull the boy from underneath her. He had blood coming from his nose, the court heard.
Tilby was so drunk that she couldn’t be woken, the court heard.
Emergency services were called and paramedics tried to revive him on the scene.
Tilby woke an hour and 15 minutes later when Darrian was already in hospital, where he later died at 5.40pm.
“It is a mother’s responsibility, a mother’s duty, a mother’s natural instinct to put the care and safety of a four-week-old baby above all else. You completely ignored that duty so you could get extremely drunk on a night out.”
Judge Paul Thomas QC
A post-mortem determined that he died from Sudden Infant Death Syndrome.
The prosecution said he had died of a heart attack, but couldn’t be certain that Tilby caused her son’s death.
Catherine Richards, prosecuting, said: “The prosecution maintain Marina Tilby was too intoxicated to take proper care of her four-week-old child.
“She was too old drunk to respond to the needs of her child; too drunk to respond to signs of distress. At the very least she lay over her child when he was already compromised.”
Tilby had previously pleaded guilty to child neglect. The court heard she had previous convictions, including one for battery in 2016.
Dyfed Thomas, defending, said Tilby will live with the grief and guilt of what she has done for the rest of her life, and suffers from depression.
Judge Paul Thomas QC told Tilby: “It is a mother’s responsibility, a mother’s duty, a mother’s natural instinct to put the care and safety of a four-week-old baby above all else. You completely ignored that duty so you could get extremely drunk on a night out.”
She will serve half her sentence before being released on licence.