This is an automatically translated article.
Professional consultation article by Doctor Department of Obstetrics and Gynecology, Vinmec Hai Phong International General Hospital.
Biparietal diameter is a very important indicator in fetal ultrasound results. Through the biparietal diameter index, doctors can determine the baby's growth and help predict the baby's weight and size at birth.
1. What is the biparietal diameter index?
BDP biparietal diameter (English name is Biparietal diameter, abbreviated as BPD) is the diameter measured at the largest cross-section (from forehead to back of neck) of fetal skull or can be understood as diameter baby's head.
Note, the biparietal diameter is completely different from the fetal head circumference. Head circumference is a measure of the circumference of the baby's head, and biparietal diameter is a measure of the diameter of the baby's head, these two parameters are like the circumference and diameter of a circle.
In fetal ultrasound, biparietal diameter is used to estimate fetal weight, calculate gestational age, and is an indicator to assess fetal growth rate.
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2. When can biparietal diameter be measured using ultrasound?
Biparietal diameter index can start measuring through ultrasound images when the fetus is 13 weeks old until about 20 weeks gestation is best. At this time, the baby's head is developing very quickly. If the fetus is large enough to measure, the accuracy will not be high anymore.
3. What is the normal BPD biparietal diameter?
The average fetal BPD biparietal diameter from 13-40 weeks of pregnancy is about 88-100mm, the mean is about 94mm.
If this BPD index is less than normal, there is a possibility that the fetus has growth retardation or the head of the fetus is flatter than in normal cases. On the contrary, if the BPD is too large, it will mean the possibility of the fetus having a large head, which can make it difficult for the mother in a normal birth, especially for mothers who have given birth for the first time. A pregnancy with a large biparietal index along with other parameters above the normal range may be the result of the mother's gestational diabetes. If the pregnancy is too large, the doctor will encourage the mother to have a cesarean section to ensure safety.
If the fetal biparietal diameter index is not within the normal range, the doctor may ask the mother to perform another ultrasound or perform further tests and tests (amniocentesis to check for DNA). ) to be sure about the health of the fetus. However, in addition to the biparietal diameter index, the doctor will combine with other indicators such as: femur length, abdominal circumference, head circumference... to make an assessment of the level of development. of the fetus, especially the development of the brain correctly.
4. Bicuspid diameter index table
| Tuổi thai (tuần) | Đường kính lưỡng đỉnh (mm) | Tuổi thai (tuần) | Đường kính lưỡng đỉnh (mm) |
| 13 | 21 | 27 | 68 |
| 14 | 25 | 28 | 71 |
| 15 | 29 | 29 | 73 |
| 16 | 32 | 30 | 76 |
| 17 | 36 | 31 | 78 |
| 18 | 39 | 32 | 81 |
| 19 | 43 | 33 | 83 |
| 20 | 46 | 34 | 85 |
| 21 | 50 | 35 | 87 |
| 22 | 53 | 36 | 89 |
| 23 | 56 | 37 | 90 |
| 24 | 59 | 38 | 92 |
| 25 | 62 | 39 | 93 |
| 26 | 65 | 40 | 94 |
5. Calculation of fetal weight according to biparietal diameter
Based on BPD, we can calculate the fetal weight according to the following 2 formulas:
Weight (grams) = [BPD (mm) – 60] x 100 For example: 90mm BPD then fetal weight (90 – 60) x 100 = 3kg. Weight (grams) = 88.69 x BPD (mm) – 5062 Example: BPD = 90mm, fetal weight: 88.69 x 90 – 5062 = 2920g.
6. How to normal fetal biparietal diameter?
When pregnant, pregnant women need to eat a balance of 4 nutritional components: protein, starch, fat and vitamins (vegetables). In which protein should focus more on strengthening for the fetus to develop well. For example, shrimp and crabs are rich in calcium and protein or can be combined with fish, beef, chicken, eggs... Pregnancy check-up and full pregnancy management. Iron supplementation : prevention of iron deficiency anemia . Calcium supplements: prevent osteoporosis for mothers and help children have enough calcium for bone development and height development. Multivitamin supplement for pregnant women to help keep the body healthy. Vaccination against tetanus for mother and child at 20 weeks of pregnancy or more: 2 doses, the 2nd dose must be given at least 1 month after the 1st dose, and the 2nd dose must be given at least 1 month before the time of birth. Biparietal diameter plays a very important role through which to determine gestational age, fetal weight, evaluate the development of the nervous system and fetal development. Pregnant women should have regular antenatal check-ups to update the fetal biparietal diameter index and detect abnormalities of this index early.
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