Fetal biparietal diameter of 9.0cm and femur length of 6.7cm at 33 weeks plus 6 days are usually normal. Biparietal diameter refers to the length of the widest part of the fetal head between the right and left sides of the head. Since there is a close relationship between the size of the fetal head and the number of weeks of gestation, ultrasound is generally used to measure the biparietal diameter of the fetal head to estimate the number of weeks of gestation and the expected date of delivery. Femoral length refers to the length of the fetal femur. The skeleton is one of the earliest fetal structures to be monitored by ultrasound. Most bones can be visualized after 15 weeks of gestation. Long bone measurements can be supplemented by long bone measurements to estimate gestational age when fetal malposition, head-in-pelvis, etc. interfere with biparietal diameter measurements. In general, the developmental criteria for a 33-week fetus are an average biparietal diameter of approximately 8.50 ± 0.47 cm and a femur length of approximately 6.42 ± 0.46 cm, and for a 34-week fetus are an average biparietal diameter of approximately 8.63 ± 0.59 cm and a femur length of approximately 6.59 ± 0.41 cm. 33 weeks plus 6 days is between 33-34 weeks, so a biparietal diameter of 9.0cm and a femur length of 6.7cm are usually normal. If a pregnant woman finds that her baby’s biparietal diameter and femur length deviate significantly from the above ranges during a pregnancy test, it is recommended that she consult a doctor in a timely manner and, under the doctor’s guidance, complete the relevant examinations to clarify the cause of the disease and provide symptomatic treatment.