With regular monitoring and carefully adjusted treatment, both before and during a pregnancy, as well as during the birth, pre-existing conditions can be controlled, and they usually carry little risk for either the mother or the fetus. Any changes in the mother’s condition that may have developed as a result of the pregnancy will normally be reversed soon after the baby has been born.
Chorionic villus sampling is usually carried out between the 10th and 13th weeks of pregnancy. Tissue from the edge of the placenta (chorionic villi) is taken and then analysed to look for a chromosomal or genetic abnormality. The risk of miscarriage is increased slightly by having this test.
Amniocentesis is usually carried out between the 15th and 20th weeks of pregnancy. A small sample of the amniotic fluid surrounding the fetus is removed and analysed for genetic abnormalities. The procedure is associated with a small risk of miscarriage (about 1 in 100 women).
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.