Prenatal diagnosis is for many parents the security without which they would not decide on having a baby. Risk pregnancies can be identified before fertilization or during pregnancy.

Stating the genotype of egg cell is possible before fertilization basing on investigation of the cells that origin during meiosis together with the egg cell. Knowledge of their genetic material is equivalent to knowledge of the egg cell genetic material (of course when woman’s genotype is known). For example for a carrier when mutant gene is found in examined cell the functional copy is in egg cell. Egg cell can be fertilized outside woman’s body (in vitro) and then implanted to the uterus. This method is useful for diseases that can be passed on by the mother. It was elaborated by dr Marylin Monk and dr Cathy Holding from Mammalian Developmental Research Unit, London.

Amniocentesis
The purpose of this inquiry is to obtain sample of foetus’s cells. It is made between 16 and 18 week of pregnancy (12 and 15 for early amniocentesis). Cells are taken by mean of a needle introduced into the uterus. It is safe for woman and carries very low additional risk of natural abortion. Taking advantage of recombinant DNA methods it is possible to state among other  the sex and karyotype of the foetus, to measure concentration of enzymes, to analyze DNA – probes enable detecting many diseases.