Hi Grannyh,
I had steroid injections (4 in total) from around 26 wks gestation. Also I was on nifedapine for about 3 weeks multple times a day. I had PE, so preterm labour was always a given with me it was just a matter of how long I could last. My DD was born @ 31 wks and was breathing on her own from the moment she popped out. Without the steroids to help mature her lungs along she may have been fully ventilated or on CPAP when born. Steroids help their lungs mature to produce surfactant. A premature baby's lungs without surfactant can be scarred by ventilation and CPAP. An example would be my sisters DD. She was born @ 26+6, with just 24-36 hours for one steroid injection to try help her along. My little neice was ventilated from birth. Home after 100 odd days in hospital and now has a condition called CLD because of the ventilation.
I cant say my DD has had any noticable side effects from either drugs that you spoke of and I was on a lot more than just those two. But for what it's worth IMO the pro's outwiegh the cons if there is a chance you are going to have a prem bub then you are better off for the baby's sake to have the steroids.