Birth Defects
What is a birth defect? Babies that survive pregnancy but are born with serious problems that threaten their health or even their lives. There are hundreds of types of birth defects, each with its own set of symptoms. Approximately 150,000 babies around the world are born each year with a birth defect. Not all birth defects are apparent at birth.
Four Major Causes of Birth Defects Environmental Hereditary Chromosomal (Errors in Chromosomes) Multifactorial (Interaction of Heredity & Environment)
Environmental Causes There are several environmental (external) factors that can affect the development of the baby. Such as: Nutritional diet of the mother Diseases or infections Harmful substances the mother consumes (prescription drugs, alcohol, illegal drugs) Exposure to hazards such as X rays
Hereditary Causes Genetics can affect the development of the baby: Every person has approx. 20,000 – 25,000 genes that determine everything from eye color to directing the growth and development of every system in the body. Children typically get 5-6 imperfect recessive genes passed on to them. Where parents both pass on the imperfect recessive gene the birth defect will appear. Tay-Sachs and cystic fibrosis are examples of such recessive inheritance.
Errors in Chromosomes Can affect the development of the baby: Several birth defects are caused by problems in the numbers or structure of chromosomes. An error may occur when an egg or sperm cell is developing, causing a baby to have too many or too few chromosomes or to have broken or rearranged chromosomes. These are NOT hereditary defects because neither parent has the abnormal chromosome. Most common birth defect of this type is Down Syndrome. (extra copy of chromosome 21)
Interaction of Heredity & Environment Some birth defects are multifactorial, meaning they are caused due to environmental and hereditary factors: The baby inherits the tendency for a birth defect to occur and is triggered by an external factor. Cleft lip and spina bifida may be caused by a combination of inherited genes and exposure during pregnancy to medications, infections, illnesses, and tobacco or alcohol.
Miscarriage and Stillbirth Sometimes a pregnancy begins, but the baby doesn’t develop normally. In some cases, the developing baby dies. If this happens prior to the 20th week of pregnancy (month 1-3) the event is called a miscarriage. If the baby dies after that time, it is called a stillbirth.
Genetic Counseling This is where a specialist evaluates : the medical histories and family history of both individuals, as well as the parents through a physical examination. they examine other family members, etc. They assess the risk of having a child with a birth defect that is caused by a defect in the genes, if there is a history of a birth defect in the family. These counselors do not tell people what to do; they only explain the options and risks.
Prenatal Tests These are tests that are conducted during a pregnancy: Alpha-fetoprotein (AFP) Blood test on the expected mother between weeks 15-20 of pregnancy. AFP is a protein produced in the liver of the fetus that is detectable in the liver of the fetus that is detectable in the mother’s blood. Abnormal AFP levels can indicate a possible birth defect. Ultrasound Uses sound waves to make a video image of an unborn baby. Helps the doctor to monitor the development of the baby, pinpoint age and detect certain birth defects (skeletal, circulatory, nervous system defects can be detected in an ultrasound).
Prenatal Tests… Amniocentesis Chorionic villi sampling A sample of the amniotic fluid is withdrawn by using an ultrasound to guide a needle through the mother’s abdomen into the amniotic sac. Some cells from the fetus are in the amniotic fluid and can be analyzed for defects such as Down Syndrome. Chorionic villi sampling A sample of tissue from the membrane that surrounds the fetus is extracted by snipping or suction, to check for specific birth defects. Detects same defects as amniocentesis, but poses a greater safety/health risk to the fetus.