1st baby came by herself.

So I had question my first baby came on her own, the nurse had asked me to push to get her down where they wanted her b4 they called for the Dr. I got her there an she called for doc. when she walked away something happened and I could feel something pushing out of me. I grabbed my MIL an said it's moving catch it! (I'm freaking out it's my first!) Dr. walks in nurses are running! No ones dressed an my baby's head is coming out! Everyone's starts yelling stop pushing! I had to nearly yell back because they weren't listening to me, that I wasn't pushing! She wanted out apparently. Dr. caught the head at the last possible second. b4 he could even get dressed. that was it. So question is what is that called? when the baby spontaneously starts to come on their own.? isn't there a medical term for it or something.? I tried to google it several times with no luck. thanks in advance, and thanks for reading