Birth Defects: Causes, Prevention, and Diagnosis, Study notes of Law

Download Birth Defects: Causes, Prevention, and Diagnosis and more Study notes Law in PDF only on Docsity! Birth Defects Rihab Abbas Ali: 2/12/2023Dr. Msc. Clinical embryology and Assisted Reproductive Technique Birth defect, congenital malformation, and congenital anomaly are synonymous terms used to describe structural, behavioral, functional, and metabolic disorders present at birth. The science that studies these disorders is teratology. TYPES OF ABNORMALITIES Malformations: occur during formation of structures, for example during organogenesis. They may result in complete or partial absence of a structure or in alterations of its normal configuration. Most malformations have their origin during the third to eighth weeks of gestation. Disruptions: result in morphological alterations of already formed structures and are due to destructive processes. Vascular accidents leading to bowel atresias and defects produced by amniotic bands are examples of destructive factors that produce disruptions. A syndrome is a group of anomalies occurring together that have a specific common cause. This term indicates that a diagnosis has been made and that the risk of recurrence is known. An association is the nonrandom appearance of two or more anomalies that occur together more frequently than by chance alone, but whose cause has not been determined. Causes of Birth Defect Malformations following maternal infection with measles, mumps, hepatitis, poliomyelitis, ECHO virus, Coxsackie virus, and influenza virus have been described. Toxoplasmosis and syphilis cause birth defects. A characteristic feature of fetal toxoplasmosis infection is cerebral calcifications. Hyperthermia Elevated body temperature (hyperthermia) is teratogenic. Defects produced by exposure to elevated temperatures include anencephaly, spina bifida, mental retardation, micropthalmia, and facial abnormalities. Hyperthermia is caused by the pyrogenic effect of the infectious agents. In addition to febrile illnesses, use of hot tubs and saunas can produce sufficient temperature elevations to cause birth defects. Radiation Ionizing radiation kills rapidly proliferating cells, so it is a potent teratogen, producing virtually any type of birth defect depending upon the dose and stage of development of the conceptus at the time of exposure. Isotretinoin (13-cis-retinoic acid), an analogue of vitamin A, used to treat cystic acne , has been shown to cause a characteristic pattern of malformations known as the isotretinoin embryopathy or vitamin A embryopathy. There is a well-documented association between maternal alcohol ingestion and congenital abnormalities, and these defects, together with mental retardation and growth deficiency, make up the fetal alcohol syndrome (FAS). The central nervous system is particularly sensitive to alcohol, and alcohol-related neurodevelopmental disorder (ARND) may result from exposure. Furthermore, alcohol is the leading cause of mental retardation. Endocrine disrupters are exogenous agents that interfere with the normal regulatory actions of hormones controlling developmental processes. the synthetic estrogen diethylstilbestrol, which was used to prevent abortion, raised the incidence of carcinomas of the vagina and cervix in women exposed to the drug in utero. Male embryos exposed in utero can also be affected, as evidenced by an increase in malformations of the testes and abnormal sperm analysis among these individuals. Oral Contraceptives. Birth control pills, containing estrogens and progestogens, appear to have a low teratogenic potential. Maternal Disease Diabetes. Disturbances in carbohydrate metabolism during pregnancy in diabetic cause a high incidence of stillbirths, neonatal deaths, abnormally large infants, and congenital malformations. Phenylketonuria. Mothers with phenylketonuria (PKU), in which the enzyme phenylalanine hydroxylase is deficient, resulting in increased serum concentrations of phenylalanine, are at risk for having infants with mental retardation, microcephaly, and cardiac defects. Spinal protrusion wy ww w 1. 2. 3. Spina bifida Spina bifida with Spina bifida with occulta meningocele myelomeningocele Obesity Prepregnancy obesity, is associated with a two- to three-fold increased risk for having a child with a neural tube defect. Causation has not been determined but may relate to maternal metabolic disturbances affecting glucose, insulin, or other factors. Hypoxia Although children born at relatively high altitudes are usually lighter in weight and smaller than those born near or at sea level, no increase in the incidence of congenital malformations has been noted. In addition, women with cyanotic cardiovascular disease often give birth to small infants, but usually without gross congenital malformations. Advanced paternal age and men younger than 20 also have a relatively high risk of fathering a child with a birth defect. Studies also show that males with birth defects themselves have a greater than twofold risk of having an affected child. Preventing and Testing for Birth Defects Eat a Healthy Diet: For example, supplementation of salt or water supplies with iodine eliminates mental retardation and bone deformities resulting from cretinism. Folate supplementation lowers the incidence of neural tube defects, such as spina bifida and anencephaly. Fortunately, folic acid is plentiful in leafy green vegetables, nuts, and citrus fruits. Head 1 | Back ——= 21 days Spina bifida  4s Spina bifida occulta Spinal protrusion 2; 3. Spina bifida with Spina bifida with meningocele myelomeningocele Avoid Infections That Cause Birth Defects Prenatal diagnosis The perinatologist has several approaches for assessing growth and development of the fetus in utero, including ultrasound, amniocentesis, chorionic villus sampling, and maternal serum screening. In combination, these techniques are designed to detect malformations, genetic abnormalities, overall fetal growth, and complications of pregnancy, such as placental or uterine abnormalities. Their use and development of in utero therapies have heralded anew concept in which the fetus is now a patient. ULTRASONOGRAPHY Ultrasonography is a relatively noninvasive technique. The approach may be transabdominal or transvaginal. Important parameters revealed by ultrasound include: characteristics of fetal age and growth; presence or absence of congenital anomalies; status of the uterine environment, including the amount of amniotic fluid; placental position and umbilical blood flow; and whether multiple gestations are present . Fetal age and growth are assessed by crown- rump length during the fifth to tenth weeks of gestation. After that, a combination of measurements, including the biparietal diameter (BPD) of the skull, femur length, and abdominal circumference are used. at eee eete TT TT Talia MATERNAL SERUM SCREENING maternal serum screening provides a relatively noninvasive technique for an initial assessment of fetal well being. One of the first of these tests assessed serum alphafetoprotein (AFP) concentrations. AFP is produced normally by the fetal liver. In cases of neural tube defects and several other abnormalities AFP levels increase in amniotic fluid and maternal serum. In other instances, AFP concentrations decrease as, for example, in Down syndrome. AMNIOCENTESIS During amniocentesis, a needle is inserted transabdominally into the amniotic cavity (identified by ultrasound) and approximately 20 to 30 ml of fluid are withdrawn. Because of the amount of fluid required, the procedure is not usually performed before 14 weeks gestation, when sufficient quantities are available without endangering the fetus. The risk of fetal loss as a result of the procedure is 1%, but it is less in centers skilled in the technique. Indication of prenatal testing: Generally, these prenatal diagnostic tests are not used on a routine basis (although ultrasonography is approaching routine use), being reserved instead for high-risk pregnancies. Indications for using the tests include: 1) advanced maternal age (35 years and older). 2) history of neural tube defects in the Family. 3) previous gestation with a chromosome abnormality, such as Down Syndrome. 4) chromosome abnormalities in either parent. 5) a mother who is a carrier for an X-linked disorder.