Head too small

Has any mommas experienced babies head being too small? I had a measurement ultrasound the other day due to my belly measuring 3 weeks ahead, I am currently 35 weeks (I have a small torso). Baby girl however is measuring in the 22 percentile and they stated her head is in the 3 percentile which raises concerns for microcephaly. But they stated that due to her positioning (head down) and my anterior placenta the measurement was most likely off. Talk about freaking a momma out.