The ultrasound is a technique that can see the embryo into the uterus of the mother. Ultrasound is emitted and its echo is received, which allows two and three-dimensional images to be generated. This way you can check the development of the fetus and detect possible malformations, in addition to knowing the sex of the baby before birth.
The Amniocentesis involves puncturing the uterus and withdrawing a small amount of the amniotic fluid surrounding the fetus. The cells of the amniotic fluid can help to know the status of the fetus, and to know if they have any chromosomal abnormalities such as Down syndrome or alterations of the spinal cord (spina bifida).
As it is an invasive test and has a small risk of miscarriage, they are usually only performed in those cases in which genetic problems are more likely to exist.
By BruceBlaus (Own work) [CC BY-SA 4.0], via Wikimedia Commons
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