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An ultrasound uses high-frequency sound waves to produce an image of an unborn baby in a womb, but the resulting photo tends to look different depending on whether it is two-dimensional (2D) or three-dimensional (3D). The standard is the 2D ultrasound, which is often the one paid for by health insurance because it can be considered medically necessary. Doctors often order at least one two-dimensional ultrasound during a pregnancy to make sure the measurements are correct for the gestational age, though it also can be used to find out the baby's sex and whether he or she displays any abnormalities. A 3D ultrasound is usually considered elective, because its main function is to offer parents a clearer image of their unborn baby. In general, a 2D ultrasound is often used for medical purposes, while a 3D ultrasound creates a keepsake for the parents.
Early in the pregnancy, doctors sometimes perform a 2D ultrasound to make sure the baby has a heartbeat and to determine the age of gestation to identify a due date. This type of ultrasound also may be used sometime during the second trimester, usually around 20 weeks. This is the point when a technician measures the unborn baby's organs and limbs to ensure they are all normal, while also making sure the umbilical cord is healthy. If he or she spots any abnormalities, the patient may be referred for further testing. For this reason, a 2D ultrasound is often considered necessary during a pregnancy and is usually paid for by health insurance, at least in the United States.
In some cases, the 2D ultrasound is considered an elective exam. For example, determining the sex of the baby is not a requirement during pregnancy, but many parents wish to do so. In many cases, this can be done during the required ultrasound around 20 weeks. If the defining characteristics can't be clearly identified at the time, though, the parents are often responsible for paying for another visit if they are determined to find out the sex. In addition, they may have to pay extra when using a 2D ultrasound to perform in-depth tests that are not considered necessary, such as determining the baby's chances of having certain genetic conditions.
Nearly all 3D ultrasounds are considered elective, leaving the parents to pay for them, often at a boutique medical clinic rather than at the doctor's office. This technology sends out sound waves from several directions, which offers a fuller picture of the baby. Unlike with a 2D ultrasound, the baby's facial features often can be clearly seen using 3D technology, especially between weeks 24 and 36. Many medical abnormalities are not clearly visible with this type of ultrasound, but the result is often a clear photo of the fetus that parents can treat as the baby's first picture, even putting it in a photo frame.