32 weeks - OB checkup

I went to my 32 prenatal appointment today. Looks like my blood pressure is fine, my urine is fine, my weight is as expected, and Lucy remains in position with a nice strong heartbeat of 150.
My OB asked whether there had been any major things that transpired since our 20 week visit. I told him about my bout of pneumonia. He wanted to know which antibiotics I took. I then told him about my frequent BH contractions, and the daily pain in the ribs I experience from Lucy which can only be alleviated by lying down. I explained how these things contrasted with my last pregnancy. He then inquired as to whether there had been a probable cause of Rebecca's premature birth. I said that nothing had ever been figured out. I had broken my water while not in labour, and that my contractions had begun almost 20 hours later. As a consequence of this discussion, he decided that I should have an ultrasound to determine whether I have a short cervix. If this turns out to be the case, I will receive corticosteroid shots to accelerate Lucy's development (especially her lungs) because it would be very likely that I would have her prematurely. I am supposed to have the ultrasound at some point next week. This condition is called cervical insufficiency or incompetence. The cervix becomes so thin from the weight of the baby that the membranes can break. In severe cases this occurs before 32 weeks and can be very serious for the baby (obviously it can also be fatal to the baby if it happens in the early second trimester). I wonder how something like this (even slightly off the average) combines with my over-separation of the pelvic bones (if at all). If you have this condition and it is caught early on, they can sew the cervix shut (yummy). At my stage, it is too late for that sort of intervention, and the drugs are the standard precautionary approach. We don't want Lucy to be born this early - while the chances of survival are extremely high at this stage (above 90% I believe), prematurity makes everything very complicated. Even Rebecca - a near-term premature baby, was extremely tired. Something as simple as drinking required tremendous energy from her - this is typical for premature babies. My OB says that in fact, the mortality rate of babies at 34 weeks is equal to that of full term babies (although obviously full term is preferable). So, now I wait for next week's ultrasound to see what I can see. In the best case scenario, I get another peek at Lucy (I think) and they might be able to guess her probable delivery weight, and nothing is wrong. In the worst case scenario, the cervix is too short, I get shots, may require bed rest and various behavioural restrictions, and leave work earlier than anticipated, and can almost certainly count on delivering yet another preemie. But, even the worst case scenario is not too grim.
All this to say, I need more data. There is no point worrying right now, but I will be extra careful just in case.