After dismissing her initial pains as Braxton Hicks earlier that morning, Jenna soon realised her contractions were barely two minutes apart.
With her husband, Josh, 28, driving, the couple along with their daughter Alana, two, tried to make their way to the hospital.
But after being stuck in horrendous school run traffic, Jenna felt her baby's head and just 10 minutes later she gave birth to daughter Sienna on September 6.
Jenna said: "When we saw all the traffic on the roads, I knew we weren't going to make it.
"Josh was trying to focus on driving but I pulled my trousers down and saw the baby's head.
"It was right in the middle of rush hour at around 8am, with all the kids heading to school.
"We had to do a u-turn back to the house while I calmly dialled for an ambulance to meet us back at the house.
"The labour pains were so intense I couldn't fight the urge to push.
"And just minutes later she was here, Sienna came out crying and I quickly placed her on my chest.
"Josh was in complete shock as he realised what had happened next to him but was trying to focus on getting us home safely.
"Once we pulled up home we all breathed a sigh of relief.
"Looking back it was such an exciting experience and Sienna was four days early."
Sienna's quick start to life hasn't all been plain sailing, despite mum Jenna claiming the pain wasn't that bad.
The mum-of-two, added: "I'd quite happily give birth again, the pain wasn't that bad at all.
"But after being checked over at hospital it was discovered that she had a faulty valve in her heart which wasn't picked up on scans.
"We spent two weeks in Birmingham Children's Hospital before being allowed home as she had two operations on her heart.
"It has all been such a whirlwind."
Jenna's and husband, Josh, a chartered account, have since been settling into life as a family of four.
The mum, who runs Sounds Right Phonic classes for kids said: "We still can't believe it all happened now.
"It was a crazy few hours but definitely worth it.
"I've been asking for a new car for a while now too so maybe I'll finally get one."