9 May 2019 The study of placental cells, which have the same chromosome constitution as the foetus, can identify the main chromosomal diseases . For example: Trisomy of chromosomes 21, 13 or 18 Diseases of sexual chromosomes Chorionic villus biopsy is performed on pregnant women in the following situations: They have an increased risk of chromosomal disease based on combined first-trimester screening. The risk corrected by combined screening is higher than expected for the mother’s age (baseline risk) The parents are carriers of chromosomal disease that can have a homozygous affect on the foetus. The pregnant woman requests it, provided that she is aware of the associated risks. There is an increased risk of chromosomal disease if the risk of combined screening is greater than or close to the risk of foetal loss due to the technique (1: 100). When is it done? Chorionic villus sampling is usually performed in the first trimester of pregnancy , up to 14 weeks. It should not be performed before 11 weeks due to the theoretical risk of amputation of the foetal limbs. It can also be done after 14 weeks , when access to the placenta is easy and amniocentesis is not possible (gestational age or position of the placenta). What are the risks? Risks of chorionic villus biopsy: Risk of foetal loss: 1:100 Risk of intra-amniotic infection: 1:500 Inconclusive result due to contamination with maternal blood: 1:1000 The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
