She also feels "violated" by what happened following the delivery at Liverpool Women's Hospital.
A midwife who appeared on a television reality show had an affair with a man whose baby she helped to deliver. Understandably, this was shocking news to the mum, who was still recovering from the major surgery.
Ms Lumsden now faces ongoing disciplinary action and is no longer employed by the hospital.
A day after the birth, she claims Ms Lumsden revealed she met her partner in Benidorm, telling of how she had "rubbed suncream" into his back. Her partner missed the birth of his first child and she claims this was because he feared his affair with Ms Lumsden would be exposed.
Rachel claims that a day after her daughter was born, when her partner had left the ward, Lumsden said she had met her partner in Benidorm on a holiday before Rachel found out she was pregnant.
The Liverpool Echo reports that a woman, Rachel (not her real name), issued a complaint against Ms Lumsden after she told the new mum that she had slept with her partner while in Benidorm. This week, in a letter, the Trust apologised for her ordeal and informed her the complaint was upheld.
When he returned he made frequent excuses for missing appointments and scans during the pregnancy, and eventually missed the birth at Liverpool Women's Hospital.
Lumsden confessed to the mother that the affair happened on a "lads holiday" to Benidorm.
Speaking to the Liverpool Echo about her ordeal, the new mother said: 'As a mum who was looking forward to the birth of her last baby, I was subjected to the most horrific ordeal any mother to be could ever imagine'.
The mum claims Ms Lumsden later called her and revealed the details of the affair - while she was still under the care of Liverpool Women's Hospital.
"This woman held my baby in her arms knowing that she had engaged in recent sexual activity with her father".
A spokesperson for Liverpool Women's Hospital Trust said: "Whilst we cannot discuss the detail of individual cases due to patient confidentiality, we can confirm that disciplinary proceedings were undertaken by the Trust as a result of two members of staff's conduct".
'The Trust took this action immediately upon being made aware of the incident and an internal investigation was also conducted.
'The disciplinary process undertaken with the members of staff involved is now being dealt with by the Nursing and Midwifery Council (NMC).
'We would like to apologise for the upset caused to the patient as a result of their experience'.
'This will haunt me for as long as I live. Ms Lumsden has not responded to requests for comment.