Ultrasound Facts in Dating a Pregnancy
Ultrasound testing during pregnancy allows physicians to monitor the development of the unborn baby and to pinpoint potential problems before birth. High-frequency sound waves scan the mother's abdomen, bouncing off the baby and the surrounding tissue to form a real-time moving picture of the baby in the womb. Because most fetuses develop within a common scale, the physician can date the mother's pregnancy by measuring different areas of the baby.
History
In 1942, two Austrian medical scientists pioneered the use of bounced sound waves in an attempt to find brain abnormalities. In the 1950s, the technology was improved and use of ultrasound technology spread rapidly in the medical community. By the 1980s, ultrasound use in obstetrics was common and today, the images relayed by the bounced sound waves offer doctors and parents-to-be an opportunity to see the unborn baby in detail.
Function
Doctors can date the approximate age of an unborn baby by measuring different parts of his body and comparing them to a national standard of fetus growth. In some cases, an ultrasound may confirm a pregnancy. By the fifth week of pregnancy, about three weeks after a woman misses her menstrual period, an ultrasound can pinpoint the gestational sac in which the fetus will grow.
Identification
During the first trimester of pregnancy, your obstetrician may take one of four different measurements to ensure that your baby is growing on schedule. Before the seventh week of pregnancy, in addition to the appearance of the gestational sac, the yolk sac becomes visible on an ultrasound. At the beginning of the seventh week, the embryo is visible and grows about 1mm every day. By the eighth week, your doctor can measure the distance from the tip of your baby's head to his behind, resulting in a crown-rump measurement.
Features
Ultrasound technology allows your doctor to take advanced measurements of your baby during the second and third trimester of your pregnancy. During this time, the length of the baby's femur (the large bone in the thigh), is measured, as well as the circumference of the baby's head and the circumference of his abdomen. In addition, your doctor may estimate the weight of your baby.
Considerations
While most ultrasounds performed during pregnancy use a hand-held transducer, positioned on the mother's abdomen, a transvaginal scan may be more accurate during the first weeks of pregnancy. A Doppler ultrasound allows the physician to adjust the sound wave sensitivity to create images of blood cells and other small areas of concern. Dynamic ultrasound machines show a three-dimensional image of the baby when a clearer image is desirable.
Tags: your baby, sound waves, unborn baby, your doctor, baby head
