Ultrasounds are used to determine everything from abnormalities, to size, and age. They are used at several different points throughout the pregnancy, and as the baby develops.
What do They Say?
An ultrasound is usually performed during different stages of your pregnancy, starting at your first prenatal visit to determine the age of the fetus and check the heartbeat. It also helps determine if there are multiple pregnancies or an ectopic pregnancy that develops outside of the uterus. At the eleven to thirteen week it may be done to determine chromosomal abnormalities, along with a blood test. It also looks at the size and position of the placenta and the amount of amniotic fluid.
Crating the Image
The ultrasound creates an image of the inside of your body using high-frequency sound waves, transmitted through the abdomen with a device called a transducer, and then recorded and transformed into video or photographic images of your baby. Ultrasound does not use radiation so is safer for you than an x-ray, therefore, it is not harmful in any way. The ultrasound is done topically on the surface of the skin using a gel as a conductive agent to aid the image quality. There is also a transvaginal ultrasound wherein a wand is inserted into the vagina and produces a greatly enhanced image quality. This is not a common prenatal practice but is sometimes used early in the pregnancy if a problem is suspected.
The next ultrasound is usually performed at eighteen to twenty-two weeks. This is a head to toe scan to look for any abnormalities. The doctor also wants to know the placenta is healthy and the baby is growing at the proper rate. They also check the heart rate and the movement of the arms and legs. You need to let the person doing the ultrasound know whether or not you wish for them to reveal the gender of the baby, because at this time in your pregnancy the ultrasound, though not foolproof, will give an indication. You may have another ultrasound closer to the end of the pregnancy to determine the position of the baby, and try to get an estimate of the birth weight.
Some women get more ultrasounds due to other complications such as diabetes or multiple births or conditions that are considered high risk, in order to assess the baby's heart rate, movements, and rate of growth on a more consistent regimen. The technician is not allowed to impart any of the findings no matter how adamant you are. They must let the doctor evaluate the results and inform you of the findings.
All in All
Although an ultrasound is a valuable tool in assessing the health of your baby, it can't do everything. In some cases the doctor may recommend amniocentesis (withdrawal of the amniotic fluid for testing) to further investigate what is happening to your baby if something is uncertain. Ultrasound cannot give an entirely accurate measure of your baby's birth weight and estimates could be off by a pound. It cannot guarantee that the baby will not have a birth defect which depends on a number of factors including size and position, the amount of amniotic fluid, and the nature of the defect. It is, however, a great tool for mother and doctor to monitor baby's progress and keep good track of their health.