Technology has come a long way in the medical field. The current medical infrastructure enables would-be parents to keep track of their baby’s growth to avert any possible complications that come in the way.
BPD or Bi-parietal Diameter and FL or femur length are two key markers of fetal growth and development in the womb. Therefore, every pregnant woman throughout their pregnancy gets an assessment of these two markers to ensure that their baby’s growth is on the right track.
These factors vary every week in the pregnancy; hence the doctors tally the fetus’ growth with the standard BPD and FL chart to ensure that the baby is in its prime health in the womb.
Since such medical terminologies can confuse first-time parents, we will discuss BPD and FL charts during pregnancy, their significance, and associated risks.
In this Article
- 1 What is Biparietal Diameter (BPD)?
- 2 What is Femur Length (FL)?
- 3 When are BPD and FL measured?
- 4 What is the BPD-FL Chart in Pregnancy?
- 5 What are the Complications of Abnormal BPD?
- 6 What are the Complications of Abnormal FL?
- 7 FAQs
- 8 Conclusion
What is Biparietal Diameter (BPD)?
Biparietal Diameter or BPD is measured during every ultrasound scan appointment throughout the pregnancy.
As the name suggests, BPD measures the diameter of the baby’s developing skull – from one side of the parietal bone to the other.
Parietal bones are shaped like curved plates and are present on either side of the skull. So, every human being is born with two parietal bones. Therefore, getting an estimate of the BPD during the ultrasound screening helps assess the baby’s gestational age.
What is Femur Length (FL)?
Femur Length or FL is another crucial marker that assesses the baby’s growth and development.
FL measures the length of the femur or the thigh bone, which is the largest bone in the human body. The length from the blunt end of the femur to the shaft analyzes if the baby is on the right growth pattern in the womb.
Anomalies to the standard femur length through the individual weeks in the pregnancy indicate underlying complications that your doctor will discuss in detail.
When are BPD and FL measured?
Unlike unique markers in pregnancy, BPD and FL are measured at every ultrasound scan that you get throughout your term.
So, the frequency of measuring the BPD and FL depends on the frequency of your ultrasound imaging. Ideally, most normal pregnancies get 1-3 ultrasound screenings leading up to the 20th week, followed by a scan once every month or every 4-6 weeks. It depends on the health of the baby and the mother and any risks associated.
During the ultrasound scan, your OBGYN will also measure two other crucial measurements, including:
- Head circumference (HC)
- Abdominal circumference (HC)
So, not only the BPD and FL, but the ultrasound technician also assesses the head and abdominal circumference to ensure that the baby’s growth is on track.
Combining all these markers, the doctor can assess two important factors:
- Gestational age
- Fetal weight
When your doctor measures these individual markers, they want to ensure that the baby’s numbers are normal and don’t involve any abnormalities.
What is the BPD-FL Chart in Pregnancy?
The BPD and FL change or increase every week throughout the pregnancy term. The BPD-FL chart serves as a standard that doctors tally to ensure that the fetus grows at a normal rate every week of the pregnancy.
Keeping track of the BPD HC AC FL normal range in cm lets us rule out multiple complications, especially the risks of dwarfish, aneuploidies, etc.
As per the standard BPD-FL chart, the normal range of BPD is 32.3 mm during 16 weeks and goes up to 96.9 mm in the 42nd week of the pregnancy.
Similarly, the FL starts at 1.5 cm during 14 weeks and 7.8 cm before delivery of the baby. The numbers might be slightly different for every baby. While slight differences aren’t concerning, drastic differences in femur length can indicate multiple birth defects.
What are the Complications of Abnormal BPD?
BPD is an important fetal measurement, so it isn’t surprising that a higher or lower range indicates certain complications.
A lower BPD measurement indicates:
- Possible risk of restrictive intrauterine growth
- Flatter and blunt development of the baby’s skull
- A sign of microcephaly
A higher BPD measurement indicates:
- Possible risk of gestational diabetes
- A possible birth defect that needs further diagnosis
According to CDC, pregnant women who have previously contracted the Zika virus should get their ultrasound done every 3-4 weeks to measure the BPD.
What are the Complications of Abnormal FL?
Unlike BPD which can raise concerns when it is both higher or lower than the normal range, the same isn’t the case with the fetal Femur Length.
A lower femur length is what causes concerns because it indicates:
Dwarfism – causes cartilage and bone growth deformities in the developing baby.
Placental insufficiency – lacking nutritional supply to the baby often leads to low FL.
Aneuploidies – causes conditions like Down’s Syndrome, Patau Syndrome, and Edward Syndrome.
Abnormalities in the femur length are often a sign of concern. Your OBGYN will assess the associated fetal measurements and then prescribe further testing to rule out any possible baby complications, especially regarding risks of birth defects.
1-What is BPD HC AC FL?
BPD, HC, AC, and FL are the four standard fetal measurements that help assess fetal growth and development and estimate the baby’s gestational age and fetal weight.
2-What is the normal BPD FL ratio?
The normal BPD-FL ratio is 79+/- 8%. Abnormalities in the BPD-FL ratio indicate risks of short-limbed dwarfism, microcephaly, hydrocephalus, etc.
BPD and FL measurements are crucial deciding factors behind the baby’s growth and overall health in the womb. Any stark abnormalities indicate risks of birth defects that your OBGYN will prescribe further testing for. Also, remember that the BPD and FL ratio is slightly different for boys and girls, leading to the differences in the numbers from the normal reference chart.
We recommend getting timely testing done as per your doctor’s prescription to rule out every possible risk associated with the baby’s growth and well-being. After all, you can never be too cautious about your baby during its gestational period.