Corticosteroid use for fetal lung maturation has been associated with decreased fetal movements and fetal heart rate variability detected by CTG over the 2 days following administration. 

Bonus Infor- corticosteroids also cause a rise in WBC Count.
When corticosteroids are administered, the  white cell count will rise 24 hours following administration of corticosteroids and should return to baseline 3 days following administration ( This is important when corticosteroids are given in PPROM).  Source- GTG- 73