#1 - 18 hours
#2 - 7 hours

In the births I've supported I tend to see a trend, with mum's who have birthed before tending to be quicker the second or third time around. The body has done it before, it knows what it's doing and the tissues and muscles, having stretched to let a baby out once don't need as long after that first birth.

That said, other factors unique to the individual birth can also come into play - the positioning of the baby etc can have a big impact on the length of labour and are specific to each individual birth.

But generally speaking, the first birth is usually the longest.