Should I be worried, or not?

My last son was born early, hes born at 34 1/2 weeks. Not really early but his lungs wasn't developed enough to breathe on his own he spent 5 days on the ventilator and 2 weeks in the NICU. Well I am 25 weeks pregnant with another boy  He is due May 23rd. My question is what are the chances of having another preemie? I had no complications during my pregnancy with my him either, & I haven't had any with this one either. My water started leaking with him & I started dilating, they have no ideal why I went into preterm labor. Thanks, in advance!

having one preemie does seem to increase the chance of having another but only when complications are involved. early spontaneous rupture of membranes is a complication and can mean a million different things, but if they found nothing wrong with you, then there really arent any answers. as long as you are following closely with your doctor and having the best pregnancy you can, you are doing fine.