B-description of the data and security

Description of the pregnancy-test b-ultrasonic measurement data

CRL--from the length of the fetal head to hips, also known as the \"head and WAIST TO HIP\". During the 8-11 week of gestation, each of the fetal development of the situation there is not much difference, so hospitals are often measured CRL to forecast production day.

BPD--head most long part between left and right sides of length, also known as the \"head in transverse diameter\". When could not be determined by CRL in the early days, often by BPD to forecasting; medium-term future, when the presumption of fetal weight and often need to measure the data.

FL--length of the thigh bones of the fetus, also known as the \"big foot long\". Thigh bone is the roots of the thigh to knee length. Generally around 20 weeks of gestation, by measuring the FL to check the condition of fetal development.

Thickness between before and after APTD--abdominal, also known as the \"before and after abdominal diameter.\" Check the State of development of the fetal abdomen and when the presumption of fetal weight, need to measure to the data.

TTD--width of the abdomen, also known as \"abdominal transverse diameter\". After 20 weeks of gestation, together with the APTD to check for fetal development. Sometimes measuring abdominal area.

B-security

B-ultrasound on fetus actually had no injuries, no authoritative findings in the medical field, can be described as controversial, most scholars believe that b-ultrasonography on fetal harm not sure. Principle analysis on b-, b-scan ultrasonic conduction is, there is no ionizing radiation and electromagnetic radiation, is a sound wave transmission, this Sonic organization no harm to the human body. But if Sonic density in a fixed place, and gathered a lot of time, there will be heating effect, when this heat effect up to a certain extent, might have an adverse effect on human tissue, affecting intracellular substances, including chromosome. Theory of high intensity ultrasonic through its high temperature and its effect on organizations of cavity, damage to organizations. But in fact, the medical use of b-ultrasound is of low intensity, less than 94 MW/cm, is no harm to the fetus, yet no b-ultrasonography of fetal abnormalities caused by reporting. At present, the hospital use of b-ultrasonography in obstetrics to the fetus is safe.

However, this does not mean that the entire b-ultrasonography during pregnancy can feel free to do, without limits of time and frequency. There are scholars have done the experiment, on 11-12 weeks of fetal eye lens and cornea of b-ultrasound irradiation, have found no radiation, no impact, exposure, five minutes, mild edema in the cornea or lens, exposure, ten minutes, edema than exposure to some five minutes, but reversible, stop after exposure to return to normal. If the exposure time of more than 20 minutes, change is not reversible. Therefore, scholars suggested that time should not exceed five minutes of a b-.