Chances of going into labour early with second baby?

My first was born at 38 weeks spontaneous rupture of membranes and spontaneous labour. He is only 7 months old and im almost 21 weeks pregnant. They will be at most 11 and a half months apart. My just wondering if having them closer together would put extra pressure on my body and sense my first was 2 weeks early could this one come early also? I know every pregnancy is different and i still may go to 42 weeks :) but i was just wondering if anyone has any input?