Biparietal Diameter Meaning in Pregnancy

Introduction

Ultrasound examinations are routinely used throughout pregnancy to assess fetal growth and development. The biparietal diameter (BPD), which refers to the distance between the two parietal bones of the fetal skull evaluated at the level of the fetal cerebral hemispheres, is one of the important characteristics examined in these exams. The BPD test is useful for determining fetal gestational age, evaluating fetal growth and development, and diagnosing probable fetal anomalies. In this post, we will look at what the biparietal diameter (BPD) means in pregnancy, how it is measured, and what the usual ranges of BPD measurements are for each week of pregnancy. We will also go through the ramifications of aberrant BPD measures as well as the significance of BPD measurements in prenatal care.

What is the Biparietal Diameter (BPD)?

The biparietal diameter (BPD) is an important characteristic evaluated during pregnancy in fetal biometry. It is the distance measured between the two parietal bones of the embryonic skull at the level of the fetal cerebral hemispheres. The BPD assessment is important for a number of reasons:

• Determining fetal gestational age: Throughout the first and second trimesters of pregnancy, the BPD measurement is one of the most accurate metrics for calculating fetal gestational age. This is because BPD is a generally stable measurement that does not alter greatly with fetal position or maternal variables.
• To assess fetal growth and development, the BPD measurement can be used in conjunction with other fetal biometry parameters such as head circumference, belly circumference, and femur length. Deviations from typical BPD ranges may suggest fetal growth limitation, macrosomia (excessive fetal growth), or other fetal disorders.
• Abnormal BPD measurements, especially when combined with other abnormal fetal biometry measurements or clinical findings, can be an indication of potential fetal abnormalities such as anencephaly (absence of major portions of the brain), hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain), or Down syndrome.

Overall, the biparietal diameter measurement is an important criterion in prenatal care since it gives important information about fetal growth and development and can aid in the identification of probable fetal problems.

How is the BPD measured?

During pregnancy, the biparietal diameter (BPD) is commonly evaluated during a normal ultrasound check. The BPD measurement is normally taken as follows:

• An ultrasound equipment is used to generate high-frequency sound waves that are transferred through the mother’s abdomen and into the fetus.

• The fetal head must be in a neutral position, which means it should not be flexed (chin to chest) or stretched (head tilted back). In some circumstances, the sonographer may gently handle the fetus or request that the mother change position in order to capture the best image.
• The sonographer will locate the fetal head and take an image of the fetal skull at the level of the fetal cerebral hemispheres. This image depicts the fetal skull’s two parietal bones, which are placed on either side of the skull.
• The sonographer will measure the distance between the two parietal bones using calipers or computerized measures. The BPD measurement is represented by this distance.

It’s important to note that the BPD measurement is usually obtained in conjunction with other fetal biometry parameters like head circumference, stomach circumference, and femur length. This enables healthcare experts to assess fetal growth and development in depth.

In summary, the BPD assessment is performed utilizing ultrasound technology with the fetal head in a neutral posture. The distance between the two parietal bones of the fetal skull is measured, and it is often conducted in conjunction with other fetal biometry studies.

What are the normal ranges for BPD measurements?

The normal range for biparietal diameter (BPD) measurements varies depending on the gestational age of the fetus. Here are the normal ranges for BPD measurements by week of gestation:

Weeks	BPD (mm)
16	32.3
16.5	34.2
17	36.0
17.5	37.7
18	39.5
18.5	41.3
19	43.0
19.5	44.7
20	46.4
20.5	48.1
21	49.7
21.5	51.4
22	53.0
22.5	54.6
23	56.2
23.5	57.8
24	59.3
24.5	60.8
25	62.3
25.5	63.8
26	65.3
26.5	66.7
27	68.1
27.5	69.5
28	70.8
28.5	72.2
29	73.5
29.5	74.7
30	76.0
30.5	77.2
31	78.4
31.5	79.6
32	80.7
32.5	81.9
33	82.9
33.5	84.0
34	85.0
34.5	86.0
35	87.0
35.5	87.9
36	88.8
36.5	89.7
37	90.5
37.5	91.3
38	92.1
38.5	92.8
39	93.5
39.5	94.2
40	94.8
40.5	95.4
41	95.9
41.5	96.5
42	96.9

It’s crucial to note that these ranges are simply estimates, and that fetuses vary slightly. Furthermore, BPD measures are most precise in the first and second trimesters of pregnancy, becoming less accurate as the pregnancy proceeds.

In summary, the appropriate range for BPD measures changes according to the fetus’ gestational age. These ranges are used by healthcare providers to measure fetal growth and development and to identify any anomalies.

Conclusion

Finally, the biparietal diameter (BPD) is an important measurement used during normal prenatal ultrasound examinations. The BPD measurement gives important information regarding fetal growth and development, and it can assist healthcare providers in identifying any abnormalities or difficulties.

As previously stated, the BPD measurement is achieved by measuring the distance between the two parietal bones of the fetal skull, and normal BPD ranges vary based on the fetus’ gestational age. These ranges are used by healthcare providers to measure fetal growth and development and to identify any anomalies.

Overall, BPD is one of numerous fetal biometry metrics used by healthcare providers to assess fetal growth and development. Healthcare providers can ensure that the fetus is growing and developing normally by monitoring the BPD and other fetal biometry parameters early in the pregnancy.

Speak with your healthcare practitioner if you have any questions or concerns regarding your pregnancy. They may give you more information about the BPD measurement and other elements of prenatal care, as well as assist you have a healthy pregnancy and baby.

Image Credits:

“File:Biparietal diameter.jpg” by Mikael Häggström. When using this image in external works, it may be cited as: Häggström, Mikael (2014). ‘Medical gallery of Mikael Häggström 2014’. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. Public Domain. or By Mikael Häggström, used with permission. is marked with CC0 1.0.