Her identical twin sister Emma Bowler-Morris had been at her side at the previous births of all her four children.
But when Emma arrived at her twin's home just minutes later, there was no time to get her to hospital. Instead she delivered her sister's baby on the bathroom floor - in the pitch dark and using just a light from her mobile phone as there had been a power cut.
Aimee, 36, says: "I'm just so glad Emma was there to help me through it. She has been with me through all the births of my children - but she never expected that she would actually deliver baby number five.
"The labour happened so quickly that I couldn't get to hospital in time. I had called an ambulance too, but Emma arrived before the ambulance and luckily she was there to deliver my son.
"We have always had an incredibly close bond - we have been able to feel when each other have been in pain. I've been able to feel her labour pains during her births, and vice versa.
"She was the perfect person to deliver my baby - she made me feel so calm despite everything that was going on. I couldn't have done it without her."
The drama unfolded in September, just three days before Aimee was due to give birth. She went into labour at her home in Llanelli, South Wales, but thought that she had plenty of time to get to hospital.
Aimee, who is separated from her husband, says: "I'd been in labour for hours with my other children, so I thought I had plenty of time to get to hospital.
"I ran a bath, but then my contractions started to speed up and soon they were just a minute apart.
"I knew then that the baby was on its way, so I phoned an ambulance and then I called Emma. She only lives around the corner from me, so she was able to come straight away. She arrived before the ambulance did."
Just to add to the complications, a sudden storm caused the electricity to be cut off to the house.
Aimee, who lives with her four other children Megan, 15, Lucas, ten, Alfie, seven, and Theo, four, adds: "The house was plunged into darkness and I was in labour. It was quite frightening.
"As soon as Emma arrived I felt the urge to push, and I knew that she was going to have to be my midwife for this birth.
"Emma was really calm about it all, which calmed me down too. She used the light from her mobile phone to see what she was doing."
A few pushes later and Aimee's son Caio arrived into the world, weighing a healthy 7 lbs 4oz. He had the cord wrapped around his neck - which is potentially life threatening - and Emma quickly untangled it.
Aimee says: "Emma was absolutely fantastic as she didn't panic at all. She took the cord from round Caio's neck and then wrapped him in a towel.
"He hadn't made a sound, so I started to panic, but Emma started rubbing his back and then finally he let out a cry. She handed him to me and put him on my chest. It was so emotional."
A few minutes after the birth, the ambulance arrived and paramedics checked mother and son over.
Aimee says: "They checked us over, but we were still in darkness. Thankfully we were both fine and we didn't have to go to hospital.
"And it's all thanks to Emma. We have always been incredibly close. I have been at the birth of her four children, and she has been with me through every birth too.
"We have always done everything together. We would always pretend to be one another at school and with boyfriends too, just to play a joke on them.
When Emma worked as a teacher and I worked in a sweet shop, all the children who didn't know she had a twin used to think they were seeing double.
The twins are so close, that they have even felt when each other has been in pain, including when they have been in labour.
Aimee says: "When I broke my arm at the age of 10, Emma felt it too, and when I had my appendix out at the age of seven.
"And when she was in labour with her first baby, I couldn't walk as I was doubled over with pain too.
"We go on separate shopping trips and come back with the same clothes, and we often turn up to meet each other in the same outfits.
"I couldn't have asked for a better midwife - and when Caio is old enough to understand I'll tell him that his special auntie brought him into the world."
Emma, who lives with husband Matthew and their four sons Benjamin, 13, Dominic, 12, Finlay, three, and Ockley, 15 months, says: '"I'm just glad I was there to be able to help Aimee."
Words by Lucy Laing