Defect, neural tube: A major birth defect caused by abnormal development of the neural tube, the structure present during embryonic life which gives rise to the central nervous system — the brain and spinal cord. Neural tube defects (NTDs) are among the most common birth defects that cause infant mortality (death) and serious disability.
There are a number of different types of neural tube defects including anencephaly, spina bifida, and encephalocele. In anencephaly there is absence of the cranial vault (the skull) and absence of most or all of the brain’s cerebral hemispheres. Encephalocele is a hernia of part of the brain and the meninges (the membranes covering it) through a skull defect. Spina bifida is an opening in the vertebral column encasing the spinal cord. Through this opening, the spinal cord and meninges may herniate to create a meningomyelocele.
All pregnancies are at risk for a neural tube defect. However, women with a history of a previous pregnancy resulting in a fetus with a neural tube defect are at higher risk. So are women with a close relative (brother, sister, niece, or nephew) who has an neural tube defect, women with type 1 diabetes mellitus, women with seizure disorders being treated with valproic acid or carbamazepine, and women or their partners who themselves have a neural tube defect.
Landmark research has revealed that 50 percent or more of neural tube defects could be prevented if women consume a folic acid-containing supplement before and during the early weeks of pregnancy in addition to the folate in their diet. The US Public Health Service, Centers for Disease Control and Prevention (CDC), and American Academy of Pediatrics recommend that all women of childbearing age who are capable of becoming pregnant should consume 400 (0.4 mg) �g of folic acid daily. Because the risk for neural tube defects is not totally eliminated by folic acid use, routine prenatal screening for neural tube defects is still advisable.
- Defect, ventricular septal (VSD)
Defect, ventricular septal (VSD): A hole in the septum (the wall) between the lower chambers of the heart (the ventricles). Ventricular Septal Defect is the most common type of heart malformation (congenital heart disease). At least 1 baby in every 500 is born with a VSD. A VSD lets blood from the left ventricle (where […]
Defensin: A family of potent antibiotics made within the body by neutrophils (a type of white blood cell) and macrophages (cells that can engulf foreign particles). The defensins play important roles against invading microbes. They act against bacteria, fungi and viruses by binding to their membranes and increasing membrane permeability. On a chemical level, the […]
- Defensive medicine
Defensive medicine: Medical practices designed to avert the future possibility of malpractice suits. In defensive medicine, responses are undertaken primarily to avoid liability rather than to benefit the patient. Doctors may order tests, procedures, or visits, or avoid high-risk patients or procedures primarily (but not necessarily solely) to reduce their exposure to malpractice liability. Defensive […]
Defibrillation: The use of a carefully controlled electric shock, administered either through a device on the exterior of the chest wall or directly to the exposed heart muscle, to normalize the rhythm of the heart or restart it.
Defibrillator: A device that corrects an abnormal heart rhythm by delivering electrical shocks to restore a normal heartbeat.