Prenatal diagnosis
The aims of prenatal medicine are diagnosis, therapy and prophylaxis. Prenatal diagnosis provides anatomical, physiological, biochemical and genetic information about the condition of the embryo and the fetus. This allows for better therapeutic care of the fetus and the newborn (perinatal medicine). Whilst diagnosis is often possible, current therapeutic interventions are limited but they are continually improving.
Pre-implantation diagnosis (PID or PGD for Preimplantation Genetic Diagnosis) extends prenatal diagnosis to the pre-implantation period. If it examines the genetic status of the polar bodies (polar body diagnosis), it can assess the maternal part of the genome. In order to examine the whole genome of the embryo, one or two cells have to be removed at the stage of blastomeres or blastocyst. The DNA can be enriched through polymerase chain reaction (PCR) and examined for genetic diseases. Fluorescence in situ hybridization (FISH) allows chromosomal parts and even individual genes to be visualized under the fluorescent microscope, for the detection of aberrations. Severe diseases such as mucoviscidosis can be diagnosed with this technique. However, there are important ethical and legal arguments against PID. Cells that are suitable for diagnosis have to be easily separable from one another. This means that embryoblast cells cannot be removed at later stages as they are already firmly attached to each other through compaction. Early blastomeric cells are suitable but they may still be totipotent and therefore may have the capacity to develop into viable embryos. This means that embryos are being produced solely for the purposes of testing, which renders the use of PID problematic.