Fetal femur length reference standard

We all know that pregnant women need to undergo multiple prenatal examinations during pregnancy. These prenatal examinations include various indicators, which are to ensure the healthy growth of the baby in the body. As the pregnancy months increase, the baby in the body will also become larger. However, babies in different months will have a growth reference standard. So what is the reference standard for fetal femur length? Let me introduce

1Comparison table of biparietal diameter and femur length

Pregnant women will undergo several examinations during pregnancy, which can determine whether the fetus is healthy and developing well. Two data play a key role, namely the biparietal diameter and femur length. Regarding the standards for biparietal diameter and femoral length, we have a comparison table for reference by mothers who need to understand the data after the examination:

2What is biparietal diameter and femoral length?

1. Biparietal diameter

The biparietal diameter is the fetal biparietal diameter, also known as BPD. Doctors often use it to observe the child's development and determine whether there is cephalopelvic disproportion and 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 in the early stage, BPD is often used to predict it; after the middle stage, this data is often also needed to be measured when estimating the fetal weight.

2. Femur length

Femoral length (FL) is an indicator commonly used by doctors to observe fetal development when performing pregnancy examinations on pregnant women using B-ultrasound (or color ultrasound).

The femur and humerus are both typical long tubular bones in the human body, and can be divided into two ends. The femur is the largest long bone in the human body and refers to the thigh bone; the humerus is located in the upper arm and is also called the upper arm bone. So as the names suggest, femur length refers to the length of the thigh bone, and humerus length refers to the length of the upper arm bone.

Femur length and humerus length are both fetal biological indicators for predicting fetal weight. However, fetal humerus length is better than femur length in predicting fetal weight.

3How to calculate fetal weight

Method for estimating fetal weight using biparietal diameter and femur length:

Method 1:

Formula: Fetal weight = 1.07*BDP*BDP*BDP+0.3*AC*AC*FL

BDP refers to biparietal diameter, AC refers to abdominal circumference, and FL refers to femur length, all in centimeters.

Method 2:

Formula: Fetal weight = biparietal diameter * 900-5200 (g)

Method 3:

The head circumference is HC, the abdominal circumference is AC, the femur length is FL, the thickness of subcutaneous fat in the fetal legs is FTH, and the estimated fetal weight is Y.

Formula 1: Y=-5168.32+100.97HC+110.86AC+143.09FL+331.43FTH

Formula 2: Y=-4973.72+260.69HC

Formula 3: Y=-2686.60+171.48AC

Formula 4: Y=-2232.56+747.42FL

Formula 5: Y=-2513.51+1049.90FTH