This happened with my first baby. Starting around 24 weeks her abdominal circumference was a little behind. I was monitored every couple weeks via ultrasound and her abdominal circumference kept falling further behind. They were worried about growth restriction. At 37+5 her abdomen measured 33 weeks and they induced me the next morning (I also had high blood pressure so this influenced their decision). She was tiny at 5lbs 13 oz but completely healthy. They'll check the umbilical blood flow to make sure the baby is ok. Don't worry too much, I'm sure the doctors will make sure your baby is ok and deliver her if they feel it's needed. Good luck, I'm sure your baby will be just fine!