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Prenatal Diagnosis - Viewing Chromosomes, Less Invasive Methods, Preimplantation Genetic Diagnosis, Genetic Counseling And The Ethics Of Prenatal Diagnosis

age risk condition fetal fetus

The future health of a new individual can be predicted, to an extent, from clues that are apparent before birth. Prenatal diagnosis is the identification of a medical condition in a developing embryo or fetus. Prenatal testing can sample fetal cells to examine DNA sequences that correspond to specific disease-causing genes or chromosomes (the structures that carry the genes). Biochemicals obtained with the fetal cell samples can also hold clues to health. Other prenatal tests analyze a pregnant woman's blood serum for telltale biochemicals that indicate the fetus faces an elevated risk of a particular condition. Ultrasound scans provide views of many aspects of fetal anatomy. Preimplantation genetic diagnosis is a technique that is actually pre-prenatal. It provides a health check on very early embryos grown in a laboratory dish, enabling parents to select those that are most likely to develop into healthy infants.

Because prenatal tests that sample fetal cells are invasive, they carry a risk of the test causing miscarriage. Therefore, these procedures are typically offered only to those pregnant women whose risk of carrying a fetus with a detectable condition is greater than the risk of miscarriage. Reasons include already having had a child or family history with a detectable genetic or chromosomal condition, or "advanced maternal age." After age thirty-five, a woman's risk of carrying a fetus with an extra or missing chromosome exceeds the risk that the procedure will cause miscarriage.

Additional Topics

Prenatal Diagnosis - Viewing Chromosomes

Biologists first tried to visualize the chromosomes in a human cell in the late nineteenth century, with estimates of the total number ranging from 30 to 80. As methods to untangle and stain chromosomes improved, the count narrowed to 46 or 48, and by 1956 was confirmed as 46, or 23 pairs. By 1959, the first chromosomal abnormalities were identified using size and crude staining patterns to distin…

Prenatal Diagnosis - Less Invasive Methods

An ultrasound scan bounces soundwaves off of the fetus to create an image. A scan is often performed after the sixteenth week of pregnancy, and the anatomy and size of the fetus is measured to see if it is growing and developing normally. The scan can often detect major structural problems, such as a malformed heart or spine. An unusual finding on an ultrasound scan can be a warning to investigate…

Prenatal Diagnosis - Preimplantation Genetic Diagnosis

Amniocentesis, CVS, and maternal serum screening are performed after a pregnancy is confirmed or in progress. In contrast, preimplantation genetic diagnosis (PGD) occurs before the embryo implants in the womb. This technique is performed on an embryo that has been derived from in vitro fertilization (IVF) and is growing in a laboratory dish. At about the 8-cell (day 3) stage, a cell is removed and…

Prenatal Diagnosis - Genetic Counseling And The Ethics Of Prenatal Diagnosis

A genetic counselor helps educate individuals, couples, and families about prenatal tests, and helps them to understand and cope with the results. The couselor also informs the prospective parents of the limitations of the tests, explaining that they can rule out certain conditions but cannot guarantee a healthy baby. Ethical issues can arise in the decision to undergo prenatal testing. For exampl…

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