Prenatal screening
Screening for Down syndrome is available to about 53.5% of mothers on a maternal age basis, and the remaining 46.5% of health boards provide serum screening for all ages.
There are several methods used in prenatal screening, these are usually used separately, and a number of factors are taken into account to determine which method should be used. Amniocentesis has been around for 20 years and is probably the most well known screening method. It involves testing a sample of the amniotic fluid surrounding the foetus, ultrasound is used to guide a needle through the abdomen, into the womb and a small amount of amniotic fluid (20ml) is removed. The procedure is usually carried out at 14-16 weeks. Amniocentesis tests for chromosome disorders, and is 99.8% reliable for chromosome number, there is however a risk of miscarriage (usually 1/250 or less) after the procedure. This is one of the reasons why amniocentesis has only been offered to over 35's (since they have a much higher risk of having a Down syndrome child)(Webb 1990).
Previous studies on amniocentesis concentrated on problems that might arise during pregnancy or immediately after, these studies found that children whose mothers had amniocentesis are more likely to have breathing problems in the first few days after birth. A study performed by Jo-Anne Finegan in Toronto followed 88 women who had, had amniocentesis, there was an increased incidence of ear infection in this group. Finegan tested the stiffness of the eardrum and found children in the amniocentesis group were more than three times as likely to have abnormal readings. It is thought that there is a disruption of the delicate balance of pressure across the eardrum when the amniotic fluid is removed, which could cause the problems(Webb 1990).
Chorionic villus sampling is another form of sampling, it involves taking a small piece of placenta and genetic testing is carried out on it, there is a slightly higher chance of foetal loss with this procedure (Dick 1996).
A more recent form of prenatal testing involves serum markers. Blood is taken from the pregnant women and the maternal blood is tested for three hormones, this test is called the 'triple screen' test. The three hormones tested are alpha foeto-protein (AFP), human chorionic gonadotrophin (HCG) and oestradiol (E3). AFP is based on the fact that Down syndrome foetuses tend to be smaller on average, have smaller placentas and thus secrete less AFP.
second, prenatal testing, is a testing of a fetus at risk for the disease. The
Amniocentesis offers many advantages to the expecting mother. This test determines whether the unborn baby has genetic or chromosomal abnormalities. It identifies several hundred genetic disorders including some of the most common such as Down syndrome and Edward’s syndrome. It can also identify other genetic disorders such as Tay-Sachs disease, Huntington’s disease, Sickle cell disease, and cystic fibrosis. Other testing techniques such as ultrasounds pick up on these problems. Only amniocentesis is able to provide the information needed to diagnosis these problems in the womb. Amniocentesis can also indicate whether the baby is at risk for spina bifida and anencephaly. The test is more than 99 percent accurate in diagnosing these various conditions. It is the only test that can provide results which are accurate. Other important reasons to have the test include checking the well being of the baby. This is important if the mother has blood sensitization, such as Rh sensitization. Also the test can determine whether the baby’s lungs are mature enough for an early delivery if the mother appears to be in premature labor.
Carrier testing is a popular option for couples who are looking to reproduce and are coming from at-risk populations. It is common for those who chose to undergo carrier testing to be aware of results or genetic disease in their family history. Prenatal testing is available to determine whether a fetus has inherited two, one from each parent, copies of the mutated gene that will cause TSD. Prenatal testing is generally utilized when both parents cannot be ruled out as carriers. Prenatal testing is performed via an assay of Hex A enzyme activity in the fetus’s cells. The cells are taken by chorionic villus sampling—when tissue is taken from the fetal portion of the placenta— or amniocentesis—where amniotic fluid is
The fetus may measure under expected weight, and with later ultrasounds, physical abnormalities may be seen. The use of an ultrasound is not a full proof method of diagnosis for trisomy 18. During the end of the first trimester, pregnant mothers are given the option of prenatal screening to assess the fetal risk of certain chromosomal abnormalities, including trisomy 18. This testing referred to as combined test, combines results from the mother’s blood and the ultrasound results. If results suggest a higher risk probability, a later more conclusive test will be scheduled. During the 15th to 18th week of pregnancy, an amniocentesis or chorionic villus can be performed to have a detailed analysis of the fetal chromosomal material which will show any abnormalities in their karyotype. There is a slight risk with both procedures of injury of the fetus or possible miscarriage. Newer testing has been developed as “non-invasive prenatal diagnosis,” which involves extracting fetal DNA from the mother’s blood sample. After birth, diagnosis is suspected based on physical attributes of the infant. As with before birth, blood testing for chromosome analysis is used for confirmation testing.
Occasionally, neonatologists are also present in the delivery room to medically intervene if there are any problems. Most of the time, expectant mothers would never encounter a neonatologist. But if complications should arise, a neonatologist is consulted to be present during and after the birth. They provide care to newborns during a cesarean or other delivery that involves medical problems with the mother or the baby. In some cases, neonatologists follow these infants for months, sometimes years after their birth to assess the long-term effects of health problems in the early stages of
There are multiple tests and doctors that may help diagnose a patient with Tay-Sachs disease. These test are organized into three groups based on when they are performed, such as preconception, antenatal, and after birth. Before pregnancy, both parents may have blood tests implemented in order to check for a hexosaminidase A deficiency. Such blood test are conducted by doing an enzyme analysis of blood or tissue. If both parents test positive for this deficiency there will be a 25% chance that the child will be affected by Tay-Sachs disease. Two types of antenatal testing may be performed in order to check the fetus for the disease, such as chorionic villus sampling and amniocentesis testing. An acceptable testing period for chorionic villus
"Prenatal genetic testing is checking for genetic disorders by looking for changes in a person's DNA" (Childress 519). Doctors take a small blood or tissue sample from a patient and they can test for genetic mutations that could possibly show up in their child. For testing for prenatal genetics, the doctor or mother wants to "determine if a fetus has genetic abnormalities likely to cause physical or mental impairments" (520 Vaughn ). If a mother is over the age of 35, the odds of her having a child with down syndrome is greater than a mother who is in her 20's. Genetic testing is also performed when there are inherited genetic disorders in the family history or ...
Prenatal tests show the possibility of a child having a genetic disorder, such as Down Syndrome which leads many parents to choose abortion. When it comes to prenatal testing there are many different testing options. Screening tests for example, which are the first tests that are done on the fetus. During the first ten to thirteen weeks of a pregnancy, a woman can get a first trimester screening done. This is an ultrasound and maternal blood test that tests for the genes of Down Syndrome and Trisomy 18. In a first trimester screening, a result of 1/50 means a woman has a 2% chance of having a baby with a chromosome disorder (The Facts on Prenatal Testing). The next testing window is the fifteenth – twentieth week of pregnancy. This is a Quad screening and consists of a maternal blood test the looks for Down Syndrome, Trisomy 1, and neural tube defects in the fetus. In this test there is a 5% false positive rate (The Facts on Prenatal Testing). Lastly, in the screening test options is the anatomy ultrasound, which is done eighteenth-twenty-second weeks into pregnancy. This screening is an ultrasound that assesses for birth defects. Screening tests are non-invasive and therefore leave very few negative impacts on the fetus. The majority of this paper will focus on the more invasive tests, such as diagnostic tests.
Prenatal genetic testing has become one of the largest and most influencial advances in clinical genetics today. "Of the over 4000 genetic traits which have been distinguished to date, more than 300 are identifiable via prenatal genetic testing" (Morris, 1993). Every year, thousands of couples are subjecting their lives to the results of prenatal tests. For some, the information may be a sigh of relief, for others a tear of terror. The psychological effects following a prenatal test can be devastating, leaving the woman with a decision which will affect the rest of her life.
Maternal serum markers tests determine the presence of pregnancy as well as the age of the fetus. The test allows the patient to be screened for the presence of fetal risk as determined by levels of alpha-fetoprotein (AFP), estriol, and human chorionic gonadotropin (Hcg) (Genetic Alliance, 2010). Maternal serum screening test is a blood test which is offered during pregnancy to determine the risks of neural tube defects, Down syndrome (trisomy 21) and Edward syndrome (trisomy 18) to the fetus. ("Pregnancy tests," 2014). During the first trimester maternal serum testing is used in combination with ultrasound to determine the risks. The test involves blood screening between 9 and 13 weeks gestations and an ultrasound
Stephen Quake, Opening the Pandora’s box of prenatal genetic testing. Nature Medicine. 17, 250-251 (2011).
There are several techniques of prenatal screening. The most common is blood testing. It is used to determine the blood type and Rh factor of a mother and the fetus. This is to prevent the complication caused by antigen-antibody reaction of Rh group of the mother and the fetus which may lead to haemolytic anemia. Besides that, blood test is also able to detect some of the blood borne diseases such as HIV, Hepatitis B, C and D and rubella. Ultrasound, on the other hand, can determine the growth and development of a fetus in the amniotic sac. It can detect structural defects such as spinal bifida and anencephaly, congenital heart defects, gastrointestinal and kidney malformations and cleft lip. Furthermore, genetic test is used to determine the chromosome condit...
Prenatal genetic screening in particular is a polarizing topic of discussion, more specifically, preimplantation genetic diagnosis (PGD). PGD is one of the two techniques commonly used to genetically screen embryos in vitro; it is usually done at the eight-cell stage of division. PGD is most often performed when there is the risk that one or both parents carry disease-causing mutations. It is extensively used by high-risk individuals trying to conceive babes who will be free of particular mutations. PGD can test for over 50 genetic conditions and even allows for sex selection if there are underlying gender-associated medical conditions. When the results are satisfactory, the selected embryo is implanted into the mother’s uterus. While a controversial technique, preimplantation genetic diagnosis is one example of some of the good genetic testing can do, more benefits will be furthe...
Technology has had a very prominent influence on electronic fetal monitoring since its appearance in the 1960’s and 1970’s. For many years, fetal monitoring was simply done by listening to a fetal heartbeat through a stethoscope. Dramatic changes in the heartbeat, such as a long period or a drop in the rate or intensity, could be detected,. Now, not only is the electronic fetal monitor used on the outside of the womb by strapping electrodes to the mother’s abdomen but electrodes can also be inserted during the first stage of labor and placed directly on the baby’s head. With advanced technologies such as this the acidity of the infant’s blood as well as the heart rate can be measured.
Newborn screening is the practice in which the harmful or potentially fatal conditions that can affect the infant's health or survival are detected. This process can prevent death or health problems and protect the infant against certain diseases and medical conditions. Newborn screening started in 1960's when many states in U.S.A. established a newborn test program for phenylketonuria (PKU) by using the Guthrie method, a system for the collection and transportation of blood samples on filter paper. Many Infants showed developments while receiving treatment. This success led to the addition of tests for other metabolic diseases. Over time, tests were added for endocrine disorders and now newborn screening program include more than 50 individual conditions.