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.
Spina bifida /ˌspaɪnə ˈbɪfɪdə/ is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy. There are three main types: spina bifida occulta, meningocele and myelomeningocele. Meningocele and myelomeningocele may be grouped as spina bifida cystica. The most common location is the lower back, but in rare cases it may be in the middle back or neck.
Liver function tests, also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient's liver. These tests include prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), albumin, bilirubin, and others. The liver transaminases aspartate transaminase and alanine transaminase are useful biomarkers of liver injury in a patient with some degree of intact liver function.
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception. Strictly speaking, the Greek term translates as "without a brain", but it is accepted that children born with this disorder usually only lack a telencephalon, the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually covered only by a thin layer of membrane—skin, bone, meninges, etc., are all lacking. With very few exceptions, infants with this disorder do not survive longer than a few hours or days after birth.
Alpha-fetoprotein is a protein that in humans is encoded by the AFP gene. The AFP gene is located on the q arm of chromosome 4 (4q13.3). Maternal AFP serum level is used to screen for Down syndrome, neural tube defects, and other chromosomal abnormalities.
Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo, which eventually forms the placenta after implantation. The presence of hCG is detected in some pregnancy tests. Some cancerous tumors produce this hormone; therefore, elevated levels measured when the patient is not pregnant may lead to a cancer diagnosis and, if high enough, paraneoplastic syndromes, however, it is not known whether this production is a contributing cause, or an effect of carcinogenesis. The pituitary analog of hCG, known as luteinizing hormone (LH), is produced in the pituitary gland of males and females of all ages.
Prenatal testing is a tool that can be used to detect some birth defects at various stages prior to birth. Prenatal testing consists of prenatal screening and prenatal diagnosis, which are aspects of prenatal care that focus on detecting problems with the pregnancy as early as possible. These may be anatomic and physiologic problems with the health of the zygote, embryo, or fetus, either before gestation even starts or as early in gestation as practicable. Screening can detect problems such as neural tube defects, chromosome abnormalities, and gene mutations that would lead to genetic disorders and birth defects, such as spina bifida, cleft palate, Down syndrome, trisomy 18, Tay–Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis, muscular dystrophy, and fragile X syndrome. Some tests are designed to discover problems which primarily affect the health of the mother, such as PAPP-A to detect pre-eclampsia or glucose tolerance tests to diagnose gestational diabetes. Screening can also detect anatomical defects such as hydrocephalus, anencephaly, heart defects, and amniotic band syndrome.
Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms; however, it increases the risk of pre-eclampsia, depression, and of needing a Caesarean section. Babies born to mothers with poorly treated gestational diabetes are at increased risk of macrosomia, of having hypoglycemia after birth, and of jaundice. If untreated, diabetes can also result in stillbirth. Long term, children are at higher risk of being overweight and of developing type 2 diabetes.
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.
Hepatoblastoma is a malignant liver cancer occurring in infants and children and composed of tissue resembling fetal liver cells, mature liver cells, or bile duct cells. They usually present with an abdominal mass. The disease is most commonly diagnosed during a child's first three years of life. Alpha-fetoprotein (AFP) levels are commonly elevated, but when AFP is not elevated at diagnosis the prognosis is poor.
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube. When the neural tube does not close completely, an NTD develops.
In oncology, AFP-L3 is an isoform of alpha-fetoprotein (AFP), a substance typically used in the triple test during pregnancy and for screening chronic liver disease patients for hepatocellular carcinoma (HCC). AFP can be fractionated by affinity electrophoresis into three glycoforms: L1, L2, and L3 based on the reactivity with the lectin Lens culinaris agglutinin (LCA). AFP-L3 binds strongly to LCA via an additional α 1-6 fucose residue attached at the reducing terminus of N-acetylglucosamine; this is in contrast to the L1 isoform. It is the L1 isoform which is typically associated with non-HCC inflammation of liver disease condition. The L3 isoform is specific to malignant tumors and its detected presence can serve to identify patients whom need increased monitoring for the development of HCC in high risk populations. AFP-L3% is now being considered as a tumor marker for the North American demographic.
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.
Fetal proteins are high levels of proteins present during the fetal stage of development. Often related proteins assume similar roles after birth or in the embryo, in which case the fetal varieties are called fetal isoforms. Sometimes, the genes coding fetal isoforms occur adjacent to their adult homologues in the genome, and in those cases a locus control region often coordinates the transition from fetal to adult forms. In other cases fetal isoforms can be produced by alternate splicing using fetal exons to produce proteins that differ in only a portion of their amino acid sequence. In some situations the continuing expression of fetal forms can reveal the presence of a disease condition or serve as a treatment for diseases such as sickle cell anemia. Some well known examples include:
AFPep is an orally-active, cyclic, 9-amino acid, peptide with a molecular weight of 969 daltons and is derived from the anti-oncogenic active site of alpha fetoprotein (AFP). Using the standard amino acid abbreviations, AFPep has the sequence cyclo(EKTOVNOGN), where O is hydroxyproline. This peptide has been shown in experimental animal models to be efficacious in the prevention and treatment of ER+ breast cancer.
Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture.
The MOMS Trial was a clinical trial that studied treatment of a birth defect called myelomeningocele, which is the most severe form of spina bifida. The study looked at prenatal and postnatal surgery to repair this defect. The first major phase concluded that prenatal surgery had strong, long-term benefits and some risks.
Sir Nicholas John Wald FRS, FRCP, FMedSci, qualified in medicine from University College London in 1967. He is currently honorary professor of preventive medicine, University College London, honorary professor, Population Health Research Institute, St George's, University of London, visiting professor, University of Oxford, and honorary consultant and adjunct professor, Brown University, Rhode Island. He was professor of environmental and preventive medicine from 1983 to 2019 at Barts and The London School of Medicine and Dentistry. He was co-founder and director of the Wolfson Institute of Preventive Medicine.
Elevated alpha-fetoprotein refers to a state where alpha-fetoprotein levels are outside of the reference range.
Limb body wall complex (LBWC) is a rare and severe syndrome of congenital malformations involving craniofacial and abdominal anomalies. LBWC emerges during early fetal development and is fatal. The cause of LBWC is unknown.
