Measuring too small outcome?

I have been measuring on track until my last appointment. I was 32+5 and measuring 29cm. My doctor called in a second opinion and that Doctor measured 28cm. They didn't  seem too concerned but sent me for an ultrasound on Monday. I will be 33+3. This is baby #2 and my son was born 6lbs3oz. If you experienced this what was your outcome?