What is the normal biparietal diameter at the expected date of delivery?

The expected biparietal diameter refers to the widest length on the left and right sides of the fetus's head, also called the great transverse diameter of the head. The doctor determines whether the child can be delivered smoothly by examining this part of the fetus. If the child's biparietal diameter is too large, it may be related to the fact that the expectant mother has better nutrition and less activity. Generally, as long as there is no abnormality in the head, there is no need to worry.

What does fetal biparietal diameter mean?

The fetal biparietal diameter refers to the length of the widest part between the left and right sides of the fetal head, also known as the "great transverse diameter of the head."

Also known as BPD, doctors often use it to observe fetal development, determine whether there is cephalopelvic disproportion, and ensure a smooth delivery.

It should reach 9.3 cm or more at full term. According to general rules, after 5 months of pregnancy, the BPD is basically consistent with the month of pregnancy, that is, at 28 weeks of pregnancy (7 months) the BPD is about 7.0 cm, at 32 weeks of pregnancy (8 months) it is about 8.0 cm, and so on. After 8 months of pregnancy, an average weekly growth of about 0.2 cm is normal. When the due date cannot be determined by CRL (crown-rump length) in the early stages of pregnancy, BPD is often used to predict it; after the second trimester, this data is often also needed to be measured when estimating the fetal weight.

What is the standard for fetal biparietal diameter?

The standard for biparietal diameter of a 12-week fetus: The fetus grows to 4.58 cm, the external genitalia begin to develop, any deformities can be revealed, and the calcification of the skull becomes more complete. The skull halo is clear, the biparietal diameter can be measured, obvious deformities can be diagnosed, and the internal organs tend to become more complete afterwards.

What to do if the fetus's biparietal diameter is too large

The larger biparietal diameter of the fetus is a sign of larger fetal development, which is directly related to the good nutrition and low activity level of the expectant mother. It shows that the adequate nutrition of the expectant mother has caused the larger development of the fetus. This is a common symptom nowadays, so there is no need to worry. As long as there is no abnormality in the fetus's head, you can rest assured.

However, if the biparietal diameter of the fetus is too large, the first thing to consider is hydrocephalus. It is recommended to pay attention to checking the fetal brain during B-ultrasound to rule out the possibility of abnormal development of the baby.

What to do if the fetus's biparietal diameter is too small

The biparietal diameter of the fetus is also directly related to the nutritional status. A small biparietal diameter may be caused by irregular menstruation, inaccurate gestational age or errors in B-ultrasound measurement. If there are no obvious developmental abnormalities, there is no need to worry too much. It is recommended to pay attention to the regularity of life and diet, pay attention to strengthening nutrition, eat more high-protein foods, and have regular physical examinations.