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The estimated date of delivery (EDD), also known as expected date of confinement, [1] and estimated due date or simply due date, is a term describing the estimated delivery date for a pregnant woman. [2] Normal pregnancies last between 38 and 42 weeks. [3] Children are delivered on their expected due date about 4% of the time. [4]
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).
The accuracy is relatively imprecise when attempted early. [15] [16] [17] After 13 weeks' gestation, a high accuracy of between 99% and 100% is possible if the fetus does not display intersex external characteristics. [18] The following is accuracy data from two hospitals:
An estimated due date is given by Naegele's rule. According to the WHO, a preterm birth is defined as "babies born alive before 37 weeks of pregnancy are completed." [ 20 ] According to this classification, there are three sub-categories of preterm birth, based on gestational age: extremely preterm (fewer than 28 weeks), very preterm (28 to 32 ...
Both abdominal and vaginal ultrasound may be used, but vaginal ultrasound allows for earlier visualization of the pregnancy. With obstetric ultrasonography the gestational sac (intrauterine fluid collection) can be visualized at 4.5 to 5 weeks gestation , the yolk sac at 5 to 6 weeks gestation, and fetal pole at 5.5 to 6 weeks gestation.
As nuchal translucency size increases, the chances of a chromosomal abnormality and mortality increase; 65% of the largest translucencies (>6.5mm) are due to chromosomal abnormality, while fatality is 19% at this size. [2] A nuchal scan may also help confirm both the accuracy of the pregnancy dates and the fetal viability.
Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. Ultrasound can be generated at very high frequencies; ultrasound is used for sonochemistry at frequencies up to multiple hundreds of kilohertz.
In the field of industrial ultrasonic testing, ultrasonic thickness measurement (UTM) is a method of performing non-destructive measurement (gauging) of the local thickness of a solid element (typically made of metal, if using ultrasound testing for industrial purposes) based on the time taken by the ultrasound wave to return to the surface.
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