Biparietal diameter minus femur length may not always be greater than 2cm in the second trimester.
The development of each fetus is not uniform, some children’s biparietal diameter is large, and some children’s femur is long, not necessarily each of the two subtracted from the average is greater than 2cm.
In the second trimester, the biparietal diameter of the fetus is usually around 9cm, and the length of the femur is usually around 7cm, and the average value of the two is around 2cm. However, the specific conditions of each fetus are different, and the biparietal diameter and femur length are affected by a variety of factors such as genetics, nutrition, etc. Some fetuses have longer biparietal diameters, and the subtraction of the two will be greater than 2cm, while some have longer femurs, and the subtraction of the two will be less than 2cm.
If there is any abnormality in the biparietal diameter and femur length of the fetus in the second trimester of pregnancy, please consult your doctor for professional guidance.