Help?

Has anyone given birth at 31 weeks? Or close to 31? I came to get an ultrasound yesterday morning and the doctor noticed my daughter is a week smaller than she went into looking further and said that my placenta isn't nurturing my daughter. So I received a steroid shot to help develope her lungs. That way when they induce me she'll be a little stronger. My question is how long do you think she may need to stay in the nicu? I'm a FTM and totally freaking out.