Amniocentesis

Abstract

Amniocentesis is the most common invasive prenatal diagnostic procedure worldwide. It is a technique of withdrawing amniotic fluid from the uterine cavity using a needle, via a transabdominal approach, under continuous ultrasound guidance, in order to obtain a sample of fetal exfoliated cells, transudates, urine, or secretions. The amniotic fluid contains amniocytes and fetal epithelial cells. Amniotic fluid can be tested directly or grown in culture for various chromosomal, bio-chemical, molecular, and microbial studies. Amniocentesis for genetic testing is generally performed between the gestational age of 16 and 20 weeks. Diagnostic amniocentesis is commonly used for prenatal diagnosis of chromosomal abnormalities, single gene disorders, fetal infection, and intra-amniotic inflammation. Common indications cited are advanced maternal age, positive maternal screening results for aneuploidy, structural abnormality on ultrasound, and inconclusive or positive noninvasive prenatal testing. Pre-procedure counseling and screening ultrasound should always be done before subjecting a woman to amniocentesis. Complete procedure is performed under ultrasound guidance with continuous visualization of the needle under proper aseptic conditions. Post-procedure follow-up includes documentation of fetal viability immediately after the procedure by ultrasound studies, anti-D immunoglobulin (300 g) to be administered to RhD negative women, and house rest for 24 h.