8 May 2019 Amniocentesis is when amniotic fluid is sampled . It entails puncturing the foetus’s amniotic sac with a needle that goes through the abdominal wall until it reaches the uterus. The needle’s path and movements are guided by ultrasound in order to avoid contact with the foetus. After the needle reaches the inside of the amniotic sac, a small amount of AF is aspirated. The body replaces the fluid in only a few hours. We then test the chromosomes in the foetal cells in the amniotic fluid, which are the same as those of the foetus. What is amniocentesis for? Amniocentesis tests for some chromosomal abnormalities with 100% accuracy. It is indicated in a number of situations: Positive combined ultrasound and biochemical screening; A chromosomal anomaly in a previous pregnancy (especially trisomy); Chromosomal abnormality in one of the parents; Morphological foetal abnormality; Unexplained early, severe restriction of foetal growth; Confirmation of non-conclusive cytogenetic result in chorionic villus biopsy; Risk of biochemical disease with diagnosis in amniotic fluid; Diagnosis of foetal infection; Older mothers. When should it be done? Amniocentesis is preferably performed between the 16th and 18th week of pregnancy , but is also possible later. Amniocentesis at 16 weeks is to avoid a higher risk of complications , especially: Miscarriage; Malformations of the foetus’s lower limbs. How long does it take? Is it painful? Amniocentesis only takes a few minutes . It is usually painless and the patient only feels the sting of the needle in the abdominal wall. The foetal heart rate is evaluated after collection of the amniotic fluid. What precautions are necessary after an amniocentesis? The patient needs to take a few days’ rest after the amniocentesis. What are the risks of amniocentesis? The risk of a miscarriage resulting from amniocentesis is about 0.5% to 1%. A miscarriage as a result of amniocentesis usually occurs in the first week after the procedure. There is also a low risk (1 in 1,000 tests ) of: Premature rupture of membranes; Infection of the foetal sac (chorioamniotitis). This article was written with the support of physicians and other clinical professionals from the Hospital da Luz network. 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.
