Twenty-nine weeks head circumference between 254.7mm ~ 289.5mm for the right size.
At 29 weeks of gestation, the average size of fetal head circumference is 272.1mm, due to the different growth and development of the fetus, there are individual differences in the size of the fetal head circumference, clinically, it is considered that the head circumference within two standard deviations above and below the average value is the normal size, therefore, the head circumference of the 29th week of gestation is between 254.7mm～289.5mm as the appropriate size.
If the head circumference of the fetus in the 29th week of pregnancy is significantly lower than the normal level of the same pregnancy, it is necessary to check the gestational week again, to clarify whether there is fetal growth restriction and other conditions; if the head circumference of the fetus in the 29th week of pregnancy is significantly more than the normal size of the same pregnancy, it is necessary to rule out whether the calculation of the gestational week is incorrect, as well as whether there is fetal hydrocephalus and other diseases.
When the head circumference of the fetus in the 29th week of pregnancy is not in line with the normal size, pregnant women should consult a doctor in a timely manner to clarify the cause of the disease, so as to avoid delaying the condition, resulting in an adverse outcome of the pregnancy.