Head circumference vs. abdominal circumference

Zoeigh
Hi Everyone! Im 37weeks pregnant and a Filipino. I underwent an ultrasound recently in a diagnostic clinic . And find out in the diagnosis section that:" (+) NOTE OF SMALL FETAL HEAD". My obgyne didn't read my result yet. But merely looking the diagnostic section makes me feel sad, worried and sick. I didnt get sick all throughout my pregnancy. Any suggestions or ideas why I have these?