Doctors can deliver hundreds of babies over the course of their professional career but in most cases, the last thing they expect is to take the birth of their child into their own hands – literally.

But California doctor Victoria Williams, 33, found herself in that very her own car.

On 2 May the family practitioner set off to Petaluma Valley Hospital's birthing centre where she is normally on call for evening and weekend deliveries, The Press Democrat reported.

Before leaving her home she contacted colleagues to let them know that her waters had broken and she was on her way in with her husband, Adam.

At first the couple was confident they would reach the hospital in time to welcome their baby to the world, but that would soon change as Victoria's contractions became – in her own words – more "guttural and grunty."

It didn't matter if the Williams were inside a moving car during rush hour traffic, the baby was ready to see the world and Victoria was going to have to deliver her own child in the passenger seat while Adam focused on getting them all to the hospital.

"I reach down and feel the head," she said. "My next thought is, 'anterior shoulder!' My last kid was eight-and-a-half pounds so I knew a big baby was a possibility ... I give slight traction downward until I feel a shoulder then I know we are all clear and rest of baby will come out just fine. I put both hands down and pull the baby up."

Victoria's second experience could not be more different from her first. Her first baby took 20 hours to deliver in her previous home while the second – who was named Kainoa – took just 40 minutes to see the light of day.

"We weren't dilly dallying at home. We didn't take our time. We left within 20 minutes. We weren't expecting 20 minutes later to have a baby," said Victoria.

The family was welcomed by hospital staff upon their arrival and Kainoa is a healthy baby girl.

Another twist in this delightfully unusual case is that Victoria got to put her own name on the birth certificate as delivering physician, which she described to WCVB-TV Boston as "pretty cool".

She added laughingly: "I think the main home point is that labour can go so many different ways. Nature can give us anything."