Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation.
Nearly every pregnant individual undergoes some type of prenatal testing. There are varying levels of simplicity, invasiveness, risk, and information that correlate to each test. These tests can be as basic as taking the mothers weight (routine) to as complex and invasive as taking internal fetal blood samples for chromosomal analysis (genetic). Routine tests are conducted repeatedly throughout an individual’s pregnancy at prenatal checkups to monitor health and progression of the mother and the baby. Genetic testing is now a common practice offered to pregnant women by their healthcare professional at specific stages of their pregnancy to test for birth defects and chromosomal abnormalities, or the possibility of carrying these genetic traits. Testing capabilities and practices are becoming safer and less invasive as this area of research continues to evolve.
The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between mother and fetus.
The triple test, also called triple screen, the Kettering test or the Bart's test, is an investigation performed during pregnancy in the second trimester to classify a patient as either high-risk or low-risk for chromosomal abnormalities.
Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood.
A nuchal scan or nuchal translucency (NT) scan/procedure is a sonographic prenatal screening scan (ultrasound) to detect chromosomal abnormalities in a fetus, though altered extracellular matrix composition and limited lymphatic drainage can also be detected.
Triploid syndrome, also called triploidy, is a chromosomal disorder in which a fetus has three copies of every chromosome instead of the normal two. If this occurs in only some cells, it is called mosaic triploidy and is less severe.
The genetics and abortion issue is an extension of the abortion debate and the disability rights movement. Since the advent of forms of prenatal diagnosis, such as amniocentesis and ultrasound, it has become possible to detect the presence of congenital disorders in the fetus before birth. Specifically, disability-selective abortion is the abortion of fetuses that are found to have non-fatal mental or physical defects detected through prenatal testing. Many prenatal tests are now considered routine, such as testing for Down syndrome. Women who are discovered to be carrying fetuses with disabilities are often faced with the decision of whether to abort or to prepare to parent a child with disabilities.
Confined placental mosaicism (CPM) represents a discrepancy between the chromosomal makeup of the cells in the placenta and the cells in the fetus. CPM was first described by Kalousek and Dill in 1983. CPM is diagnosed when some trisomic cells are detected on chorionic villus sampling and only normal cells are found on a subsequent prenatal test, such as amniocentesis or fetal blood sampling. In theory, CPM is when the trisomic cells are found only in the placenta. CPM is detected in approximately 1-2% of ongoing pregnancies that are studied by chorionic villus sampling (CVS) at 10 to 12 weeks of pregnancy. Chorionic villus sampling is a prenatal procedure which involves a placental biopsy. Most commonly when CPM is found it represents a trisomic cell line in the placenta and a normal diploid chromosome complement in the baby. However, the fetus is involved in about 10% of cases.
Maternal–fetal medicine (MFM), also known as perinatology, is a branch of medicine that focuses on managing health concerns of the mother and fetus prior to, during, and shortly after pregnancy.
Percutaneous umbilical cord blood sampling (PUBS), also called cordocentesis, fetal blood sampling, or umbilical vein sampling is a diagnostic genetic test that examines blood from the fetal umbilical cord to detect fetal abnormalities. Fetal and maternal blood supply are typically connected in utero with one vein and two arteries to the fetus. The umbilical vein is responsible for delivering oxygen rich blood to the fetus from the mother; the umbilical arteries are responsible for removing oxygen poor blood from the fetus. This allows for the fetus’ tissues to properly perfuse. PUBS provides a means of rapid chromosome analysis and is useful when information cannot be obtained through amniocentesis, chorionic villus sampling, or ultrasound ; this test carries a significant risk of complication and is typically reserved for pregnancies determined to be at high risk for genetic defect. It has been used with mothers with immune thrombocytopenic purpura.
Trisomy 16 is a chromosomal abnormality in which there are 3 copies of chromosome 16 rather than two. It is the most common trisomy leading to miscarriage and the second most common chromosomal cause of it, closely following X-chromosome monosomy. About 6% of miscarriages have trisomy 16. Those mostly occur between 8 and 15 weeks after the last menstrual period.
Circumvallate placenta is a rare condition affecting about 1-2% of pregnancies, in which the amnion and chorion fetal membranes essentially "double back" on the fetal side around the edges of the placenta. After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface. Circumvallate placenta is a placental morphological abnormality associated with increased fetal morbidity and mortality due to the restricted availability of nutrients and oxygen to the developing fetus.
Prenatal sex discernment is the prenatal testing for discerning the sex of a fetus before birth.
Ravinder (Rav) Dhallan is the chairman and chief executive officer of Ravgen.
For preventing Tay–Sachs disease, three main approaches have been used to prevent or reduce the incidence of Tay–Sachs disease in those who are at high risk:
L1 syndrome is a group of mild to severe X-linked recessive disorders that share a common genetic basis. The spectrum of L1 syndrome disorders includes X-linked complicated corpus callosum dysgenesis, spastic paraplegia 1, MASA syndrome, and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS). It is also called L1CAM syndrome and CRASH syndrome, an acronym for its primary clinical features: corpus callosum hypoplasia, retardation, adducted thumbs, spasticity, and hydrocephalus.
A termination for medical reasons (TFMR) is an induced abortion motivated by medical indications involving the fetus or mother. In most countries, health risks are the only basis for obtaining a legal abortion. Prenatal screening can allow early diagnosis, and abortion if desired or necessary. Some medical organizations advocate the offer of diagnostic testing by chorionic villi sampling, and amniocentesis to all pregnant women, as a matter of course.
Rh factor testing, also known as Rhesus factor testing, is the procedure of determining the rhesus D status of an individual.
Noninvasive prenatal testing (NIPT) is a method used to determine the risk for the fetus being born with certain chromosomal abnormalities, such as trisomy 21, trisomy 18 and trisomy 13. This testing analyzes small DNA fragments that circulate in the blood of a pregnant woman. Unlike most DNA found in the nucleus of a cell, these fragments are not found within the cells, instead they are free-floating, and so are called cell free fetal DNA (cffDNA). These fragments usually contain less than 200 DNA building blocks and arise when cells die, and their contents, including DNA, are released into the bloodstream. cffDNA derives from placental cells and is usually identical to fetal DNA. Analysis of cffDNA from placenta provides the opportunity for early detection of certain chromosomal abnormalities without harming the fetus.
