33 weeks pregnant, smaller than the ultrasound head equivalent to 23 weeks
The average biparietal diameter of a child at 33 weeks of gestation should be around 8.2 to 8.3cm and the femur length should be around 6.4cm. Your ultrasound results suggest that the child's biparietal diameter is 24 weeks then you are worried about fetal microcephaly. The most reliable indicator for diagnosing small head malformation in children is that the size of the biparietal diameter and head circumference is less than 3 times the standard deviation of the normal value.The diagnosis can be confirmed by measuring the head circumference and biparietal diameter through ultrasound.
If the pregnancy is 33 weeks and all other tests are consistent with the time of three weeks of pregnancy, but the fetal head is small, indeed only equivalent to 23 weeks, consider the fetal developmental malformation as microcephaly.It is recommended to further review at the higher hospital to clarify the diagnosis and then consider the next treatment advice.
According to your description, in general, thirty-three weeks of pregnancy, to do ultrasound examination fetal head small, equivalent to the size of 23 weeks of pregnancy, so there is still the possibility of malformation, or that the fetal development is slow, it is best to go to two tertiary hospitals to check to confirm the diagnosis, if there is indeed a problem, or need to be carefully considered.