Anyone with multiple preemie babies?

My first baby was born at 27 weeks weighing 2lb 4oz the cause was unknown. My son was in NICU for 13 weeks and while I was there one woman was with her THIRD time premature baby, her first born was at 34 weeks, second pregnancy baby born at 31 weeks and third was born at 28 weeks! I am pregnant with my second baby now and wondered how common it is for woman to give birth to preemie babies again?

Below is pictures of my first born after 1 week and a current picture just to show all you ladies how amazingly strong these preemies are!