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After 13 weeks of gestation, the fetal age may be estimated using the biparietal diameter (the transverse diameter of the head, across the two parietal bones), the head circumference, the length of the femur, the crown-heel length (head to heel), and other fetal parameters.
Ultrasonography involves an algorithm that incorporates biometric measurements of the fetus, such as biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL), to calculate the estimated fetal weight (EFW). [32]
An ultrasound showing an embryo measured to have a crown-rump length of 1.67 cm and estimated to have a gestational age of 8 weeks and 1 day. Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump).
From this, the size of the head and the fetal weight can be determined with incredible accuracy. The use of ultrasound cephalometry is meant to be used in addition to other radiographic techniques. Thus far, no ill effects have been reported to the fetus or the mother using the ultrasound fetal cephalometry. [4]
The most common sign is a head circumference above the 90th percentile. ... the invention of prenatal ultrasound made diagnosis of fetal hydrocephalus possible around ...
Third-trimester obstetric ultrasonography (head circumference, femur length) ±8% of the estimate As a general rule, the official gestational age should be based on the actual beginning of the last menstrual period, unless any of the above methods gives an estimated date that differs more than the variability for the method, in which case the ...
The greatest circumference of the head, which corresponds to the plane of the occipitofrontal diameter, averages 34.5 cm (13.6 in), a size too large to fit through the pelvis without flexion. The smallest circumference, corresponding to the plane of the suboccipitobregmatic diameter, is 32 cm (13 in).
During his training, he worked with Ian Donald, who had published some of the first papers on the use of ultrasound in obstetrics. Together, they published multiple papers on fetal biometry and developed charts of fetal measurements such as the biparietal diameter and head circumference. Their collaboration led to methods for estimating the ...