A fetus that is 3 weeks small is not necessarily growth restricted.
Whether or not a fetus is growth restricted should be compared with the normal values for a fetus of the same gestational week. The first step is to check the gestational week, and an ultrasound examination will usually be used to determine whether or not the fetus meets the criteria for growth restriction.
The biparietal diameter, head circumference, abdominal circumference, and femur length are measured. If the biparietal diameter, head circumference, abdominal circumference, and femur length are not less than the 10th percentile of the normal values for a fetus of the same gestational week, the fetus does not have growth restriction.
If one or more of the biparietal diameter, head circumference, abdominal circumference, and femur length are below the 10th percentile of normal values for a fetus in the same gestational week, fetal growth restriction is diagnosed and further investigation is needed to determine the cause.
In conclusion, if the fetus is small in size, it is necessary to go to the hospital in a timely manner for relevant examinations to identify the cause of the disease and then give targeted treatment and therapy.