TTC after premature birth

My son was born and passed away 3 weeks ago. He was born at 24.5 weeks and the reason I went into premature labor was because of a sub chorionic hematoma I had since I was 6 weeks pregnant. My first pregnancy was full term and healthy. My doctors seem optimistic that this would not happen again with a subsequent pregnancy. Have any of you had experience getting pregnant again after an SCH pregnancy? Since my son was born at 24 weeks do we still need to wait the usual 18 months-2 years before TTC again, or can you try again sooner after a PPROM?