Steriod injection.

Hi guys..this is my fisrt pregnancy 34 weeks 3 days with twins and my gynea said she will give steriod injection to me which will help baby twin girls to breathe normal when they delivered..these injections will help their lungs to work properly...

I am just nerveous that every twin mom take steriods injection or its just normal..if so how many injection will be given to us? Or any other side effects..? Or if we dnt take that injections what will happen..sorry about foolish questions..but just need information..thanks..