Amniocentesis

Amniocentesis (also referred to as an amniotic fluid test) is a medical procedure used primarily in prenatal diagnosis of chromosomal abnormalities and fetal infections, as well as for sex determination. In this procedure, a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus. The fetal DNA is then examined for genetic abnormalities. The most common reason to have an 'amnio' performed is to determine whether a fetus has certain genetic disorders or a chromosomal abnormality, such as Down syndrome. Amniocentesis (or another procedure, called chorionic villus sampling (CVS)) can diagnose these problems in the womb.These prenatal examinations can prove helpful to expectant guardians as they allow for evaluating the fetal health status and the possibility of treatment feasibility. An amniocentesis is performed when a woman is between 14 and 16 weeks gestation. Women who choose to have this test are primarily those at increased risk for genetic and chromosomal problems, in part because the test is invasive and carries a small risk of miscarriage. This process can be used for prenatal sex discernment and hence this procedure has legal restrictions in some countries. Amniocentesis (also referred to as an amniotic fluid test) is a medical procedure used primarily in prenatal diagnosis of chromosomal abnormalities and fetal infections, as well as for sex determination. In this procedure, a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus. The fetal DNA is then examined for genetic abnormalities. The most common reason to have an 'amnio' performed is to determine whether a fetus has certain genetic disorders or a chromosomal abnormality, such as Down syndrome. Amniocentesis (or another procedure, called chorionic villus sampling (CVS)) can diagnose these problems in the womb.These prenatal examinations can prove helpful to expectant guardians as they allow for evaluating the fetal health status and the possibility of treatment feasibility. An amniocentesis is performed when a woman is between 14 and 16 weeks gestation. Women who choose to have this test are primarily those at increased risk for genetic and chromosomal problems, in part because the test is invasive and carries a small risk of miscarriage. This process can be used for prenatal sex discernment and hence this procedure has legal restrictions in some countries. Several researchers worked on the development of amniocentesis for fetal sex determination in the 1950s. Between 1959 and 1967, Robert Lisle Gadd developed the new technique of amniocentesis for clinical assessment of fetal wellbeing in utero. He presented his results at the William Blair-Bell Memorial Lecture at the RCOG in London in 1965 and was awarded an MD from the University of Manchester for this work. He also described amniocentesis techniques, as well as other details about amniotic fluid, in the chapter 'The Liquor Amnii' in the 1970 and 1977 editions of Scientific Foundations of Obstetrics and Gynaecology. Up to the mid-1970s amniocentesis procedures were done 'blind‘. Doctors Jens Bang and Allen Northeved from Denmark were the first to report amniocentesis done with the guide of an ultrasound in 1972. Chorionic villus sampling (CVS) was first performed by Italian biologist Giuseppe Simoni in 1983. Real-time ultrasound is now used during all invasive procedures because it provides for the safety of the fetus and accuracy of results. Early in pregnancy, amniocentesis is used for diagnosis of chromosomal and other fetal problems such as: Amniocentesis can predict fetal lung maturity, which is inversely correlated to the risk of infant respiratory distress syndrome. Fetal lung maturity can be tested by sampling the amount of surfactant in the amniotic fluid in pregnancies greater than 30 weeks. Several tests are available, including the lecithin-sphingomyelin ratio ('L/S ratio'), the presence of phosphatidylglycerol (PG), or the surfactant/albumin (S/A) ratio. Amniocentesis can detect infections via decreased glucose level, a Gram stain showing bacteria, or abnormal differential count of white blood cells. Amniocentesis can be used to diagnose Rh incompatibility, a condition when the mother has Rh-negative blood and the fetus has Rh-positive blood. Early detection is important to treat the mother with Rh immune globulin and to treat her baby for hemolytic anemia. Polyhydramnios, or the accumulation of amniotic fluids which leads to increase risk of cesarean section, can be relieved via decompression amniocentesis. Amniocentesis can also be used to diagnose potential causes of polyhydramnios.