Steroid injections for lung development

I will be going for my next check up and ultrasound on the 12th of March, I will be 25weeks +1day and my doctor said she will be giving me a steroid shot that day. I have had it with my 3rd child. But I feel I don’t want to get it with my 4th if I have no signs of going into early labour. All my pregnancies were full term except for one I had a miscarriage at 20weeks due to a shortened cervix. My cervix was measuring very long last time I went for an US so I don’t see the need for the steroid injection. My sugar was high the last time I went to see my doc. Even though she said it’s not gestational diabetes. I’m worried it can spike it even further and I’ve read other things that could happen. I know it’s worth it if baby has to come preterm but I don’t know why, I just feel I shouldn’t get it this time. What are your thoughts? I’m definitely not against it, but for me, having high sugar, it might cause more harm than good.