I only had the one set of steriods and my doctor never suggested another one (my circumstances were different since i was given the first dose at 31 weeks) but online says it can be a common practice if the mother does not give birth within 14 days of receiving the initial dose...
I read a couple articles on it and this is what I have found..
Potential down sides to multiple doses can include: psychomotor delays, behavioral problems and the fact that the effects on neonatal mortality aren't known between the single and multiple dose courses. In separate findings by an Israeli study it was also noted that there is an increase in maternal infection with the use of steroids, so limiting doses may help with this side effect as well.
Murphy's team found that women given multiple doses of corticosteroids had babies that weighed less, were shorter and had smaller head circumference than babies of mothers given a placebo.
Also, there was no difference in other results, such as death, respiratory problems and bleeding in the brain between the babies of women given more than one dose of steroids and women given a placebo, the researchers reported.
It seems there really hasnt been alot of studies on it in either direction though.
Ultrasounds don't hurt baby-- if they're done for long amounts of times (IE they leave the wand in the exact same spot for hours) it can damage soft tissues, but ultrasound is nothing more than sound waves. Women have weekly ultrasounds done their entire pregnancy with positive results.
As for steroid shots (I'm not 100% on this as I've never had it done) but women with preterm issues have had them done to help try and mature the babies lungs. I don't think having it done twice is abnormal, but I'm sure others who have had it will respond.