Every pregnant woman wants to know her due date. But a due date calculated from last menstrual period with a due date calculator often doesn't match the due date that is estimated by ultrasound also known as a sonogram. During an ultrasound, a technician spreads a warm gel over the lower part of the abdomen, and then presses a tool called a transducer against the belly to examine the fetus using sound waves. An image of the fetus appears on an accompanying computer screen. While looking at this image, the technician takes some standard measurements from different angles and listens for a heartbeat.
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Fortunately for the curious and anxious alike, pregnancy ultrasounds are a very standard — and very welcome — part of prenatal care. An ultrasound is a type of technology that uses sound waves to create images. During pregnancy, a transducer or wand is placed in your vagina or on top of your belly. The transducer then picks up these echos and translates them into the image of your baby that you see on the screen. Later, ultrasounds screen for fetal growth and placenta location, as well as a baby's general health and anatomy. Toward the end of pregnancy, ultrasounds can be useful for checking the length of your cervix if there is any suspicion that you may be in preterm labor as well as verifying that your baby is in a heads-down position before labor.
The first ultrasound, done between six to ten weeks in your pregnancy, is considered the most accurate method to predict your due date. If the estimated due date calculated from the first ultrasound is different from the one calculated by LMP, the doctor will consider the due date from the ultrasound as more accurate. During the first 20 weeks of pregnancy, the margin of error is roughly 1. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.
The results of ultrasound testing provide you and your health care provider with critical information about you and your baby. See below for descriptions of the information gathered from these two types of ultrasounds. Ultrasound uses high-frequency sound waves to create images of the inside of the body. The technique does not use any radiation. It is safe, painless and relatively quick test that usually takes around 30 minutes.