I had those horrid steriod injections for the baby's lungs and the oral medication to stop the labour (can't remember what this was) My dr monitored me very closely and gave me an U/S in her office every visit.
On her advice I cut back my hours at work to 10-4. Stopped the travelling totally and prayed that he would hang on.
My Dad passed away 2 weeks before my pre term labour so I believe he was looking after us.

Sometimes there is no rhyme or reason why things happen.