Pre Natal Screening

Prenatal screening is carried out to identify the fetus, at risk of being born with an abnormality or any disorder. It allows parents to be fully informed of the potential risk of giving birth to a deformed child and the further consequences. Combined with appropriate prenatal counselling, decision can be made about the continuation of the pregnancy.

Prenatal screening identifies:

  • Maternal medical conditions that left untreated, could potentially harm the baby in utero, or after birth

  • Congenital, genetic or chromosomal abnormalities in the fetus including birth defects

  • The sex, age and growth of the fetus

Certain prenatal tests are offered routinely to all pregnant women. Other special tests are reserved for high risk pregnancies, such as:

  • Women becoming pregnant first time after 35 years or older
  • Teen age pregnancies
  • Previous history of prematurity
  • Previous history of birth defect
  • Multiple pregnancies
  • Women with previous medical conditions, like high blood pressure, diabetes, lupus, heart disease, kidney problems, cancer, a sexually transmitted disease or seizure
  • Who come with a family history of genetic disorder or chromosomal abnoramalities or consanguinity marriages

Prenatal tests include the following:

    A. Routine Biochemical Tests - Blood test for anemia, blood group Rh typing, blood sugar, blood for infectious disease screening (TORCH screening), HIV, hepatitis and syphillis.



    B. Routine Ultrasound - This provides information about the normal growth of the fetus, number of the fetuses, if any chromosomal abnormalities, record foetal heartbeat, breathing movements including the expected time of delivery.


    C. Biochemical Maternal Serum Screening- These screening tests are capable of detecting fetal abnormalities such as Down's Syndrome, Spina Bifida and many more. The screening includes:

    • First Trimester Screening
    • Triple Marker Screening/ Quadruple Marker Screening

      • 1. First Trimester Screening
      a. Biochemical screening- Here the maternal blood is taken to assess the fetal risk of having chromosomal or any other abnormalities which includes b-human chorionic gonadotrpin (b-HCG) and PAPP-A, two biochemical markers which are increased in the first trimester in affected pregnancies. Screening programs, combining with advanced maternal age with these two markers in the first trimester will detect 60-68% of Down's Syndrome babies. But the sensitivity of this screening method is less as compared to the second trimester screening.

      b. Unltrasonography- Here the nuchal translucency measuremnet detects the Down's syndrome up to 77% but combining biochemical screening with nuchal translucency test will increase the sensitivity to 90% with false positive of 5%.

      The blood screening test is done between 11-13th weeks..

      2. Triple Marker Screening/ Quadruple Marker Screening:
      The triple screen test is performed between the 15th and 20th week of pregnancy. The triple screen test is a maternal blood screening test that looks for three specific substances: AFP, hCG, and Estriol.

      • AFP: alpha-fetoprotein is a protein that is produced by the fetus.
      • hCG: human chorionic gonadotropin is a hormone produced within the placenta
      • Estriol: estriol is an estrogen produced by both the fetus and the placenta
      • The level of an additional substance — inhibin-A — is also measured with the above mentioned proteins through the same non-invasive procedure with blood sample.

        • According to American Pregnancy Association, the triple screening test is strongly advisable to women who:

      • Has a family history of birth defects
      • Is pregnant first time at the age of 35 years or older
      • Used possible harmful medications or drugs during pregnancy
      • Has diabetes and use insulin
      • Had a viral infection during pregnancy, like Rubella and others
      • Has been exposed to high levels of radiation




        • High levels of AFP may suggest that the developing fetus has a neural tube defect such as spina bifida or anencephaly. However, inaccurate dating of the pregnancy can also give higher level of AFP.

        Low levels of AFP and abnormal levels of hCG and estriol indicate that the developing baby has Trisomy 21( Down's syndrome), Trisomy 18 (Edward's Syndrome) or another type of chromosome abnormality.

        In Down’s Syndrome pregnancies, maternal serum inhibin- A concentration have been found to be elevated in the second trimester of pregnancies.

        Although the primary reason for conducting the test is to screen for genetic disorders, the results of the triple screen can also be used to identify:

      • A multiples pregnancy
      • Pregnancies that are more or less advanced than thought

      • It is important to remember that the first trimester/ triple/ quadruple screenings are the screening tests and not diagnostic tests. Thes tests only note that a mother is at increased risk of carrying a baby with a genetic disorder.

        Integrated serum screening test which invloves combining screening in both first and second trimester, reaches the detection rate of 94% with false positive rate of 5%. This include first trimester nuchal translucency by scan plus PAPP-A with second trimester AFP, serum estriol and HCG measurement which may be favoured by older women wishing to obtain as much information as possible before undergoing any invasive diagniostic testing like CVS or amniocentesis with all inherent risk involved.

        •  

    D. Confirmatory Tests- For correct diagnosis, the chromosomes of the fetus must be examined by the follwoing procedures:

    • Chorionic Villus Sampling (CVS)
    • Amniocentesis


      • 1. Chorionic Villus Sampling (CVS)

      Chorionic villus sampling (CVS) is usually performed between 10 and 13 weeks of gestation and involves aspiration of placental tissue. CVS is performed using either percutaneous transabdominal or the transcervical approach. Transabdominal CVS is performed at gestations greater than 13 weeks.

      There is a consensus that CVS, both transabdominal and transcervical, has to be performed under continuous ultrasound control. Techniques for transabdominal CVS vary significantly both in the size of the needle used (e.g. 18-gauge, 20-gauge, double needle 17/19-gauge, double needle 18/21- gauge) and method of aspiration (e.g. negative pressure by syringe, negative pressure by vacuum aspirator, biopsy forceps). As there are no published studies comparing clinical outcomes using different techniques, clinicians are advised to use the technique with which they are familiar. The same applies to transcervical CVS: although there is some evidence to support use of small forceps as opposed to aspiration cannulae, the evidence is not strong enough to support change in practice for clinicians familiar with aspiration cannulae.

      Unfortunately, there are no studies that compare CVS with no testing. Randomised trials comparing CVS by any route with second trimester amniocentesis showed an excess pregnancy loss of 3%. However, only one randomised trial compared transabdominal CVS with second-trimester amniocentesis and found similar total pregnancy loss (6.3% versus 7%).

      Several other randomised trial studies show almost identical miscarriage rates after transcervical CVS compared with the transabdominal approach. Only the trial from Denmark found the transabdominal approach to be significantly safer but operator experience in the two techniques differed. Interestingly, meta-analysis comparing transcervical CVS with second-trimester amniocentesis showed amniocentesis to be significantly safer (excess miscarriage rate of 3% associated with CVS).



      2. Amniocentesis

      Amniocentesis is the most common invasive prenatal diagnostic procedure undertaken in the UK. Most amniocenteses are performed to obtain amniotic fluid for karyotyping and the majority are undertaken from 15 completed weeks (15+0) onwards. Amniocentesis performed before 15 completed weeks of gestation is referred to as ‘early.

      Amniocentesis is associated with higher rates of successful taps and lower rates of ‘bloody’ taps when performed under direct ultrasound control with continuous needle tip visualisation. The method of amniocentesis used has been described variously in the literature. Normally, a ‘blind’ procedure involves palpating the outline of the uterus and inserting a needle into a selected spot. With ‘ultrasound guidance’, the contents of the uterus, particularly the position of the placenta, are visualised prior to amniocentesis and a suitable point on the mother’s abdomen marked. The ultrasound probe is then removed from the abdomen and the needle inserted through the mark.

      Although this technique allows the operator to assess the feasibility of the amniocentesis, it does not ensure the safety of the fetus. In contrast, the use of real-time equipment allows the insertion of the needle under ‘continuous ultrasound control.’ Improvements were evident by undertaking amniocentesis under ‘continuous ultrasound control’ compared with ‘ultrasound guidance’. Continuous visualisation of the amniocentesis needle by ultrasound reduced blood-staining from 2.4% to 0.8%.

      The best estimate of a miscarriage risk associated with amniocentesis comes from a randomised trial from Denmark reported in 1986. This study randomised 4606 low-risk women aged 24–35 years to have or not to have an amniocentesis, which was carried out using a 20-gauge needle under real-time ultrasound guidance. Most procedures were performed at between 16 and 18 weeks of gestation. The amniocentesis group had a loss rate which exceeded the control group by 1%, a figure which is often quoted in counselling.

      Several more recent large uncontrolled series suggested that procedure-related loss rates around 0.5% can be
      achieved. There is debate, however, on what constitutes a procedure-related loss, particularly relative to the
      time interval after the procedure. Practitioners should be aware of these issues and, if quoting lower loss rates
      than 1%, should be aware of the adequacy of their own follow-up data.

    E. Genetic Counselling -

    The interpretation and risk assessment of the prenatal analysis and later the confirmatory diagnosis need to be explained to the parents by a genetic counselor. The best time to seek genetic counseling is before becoming pregnant, when a counselor can help assess your risk factors. But even after you become pregnant, a meeting with a genetic counselor can still be helpful. For example, when a baby is diagnosed with spina bifida before birth. Recent research suggests that delivering a baby with spina bifida via cesarean section (avoiding the trauma of travel through the birth canal) can minimize damage to the spine — and perhaps reduce the likelihood that the child will need a wheelchair.

    Experts recommend that all pregnant women, regardless of age or circumstance, be offered genetic counseling and testing to screen for Down's syndrome.

Eastern Biotech & Life Sciences offers comprehensive pre natal screening with genetic counseling. The genetic consultations may be conducted either through email, telephone call arranged by us or where possible, in person co-ordinate by our staff.

Please contact us for further details at: 04 3692061 or email us: info@eastrenbiotech.com
 

News:

  1. Breakthrough in prenatal screening for Down's syndrome ( The Medical News, Jan, 2009)

    2. Lenetix announced a significant step in the development of an improved first and second trimester non-invasive fetal chromosomal screening test to detect Down's syndrome and other genetic fetal conditions in January, 2009. The maternal serum test developed by Lenetix medical director Dr. Stephen A. Brown at the University of Vermont incorporates the use of methylation-sensitive amplification (MSA) of fetal nucleic acid markers. In the preliminary studies, more than ten clinical plasma specimens of various ethnicities provided by clinical partners were tested with clinical partners using the MSA approach developed by Dr. Brown. Data from pilot studies indicate that highly accurate screening for common fetal autosomal (Trisomy 18, 21) and sex chromosomal (47, XXY) chromosome abnormalities is feasible, particularly in the first trimester of pregnancy when MSA features of early pregnancy-derived cells can be leveraged. This approach affords diagnostic confirmation by CVS, an invasive first trimester procedure, or genetic amniocentesis in the early 2nd trimester.

    "The technique described by Dr. Brown and his team at Lenetix will create a revolution in prenatal diagnosis," said study investigator Allan Fisher, M.D., FACOG, FACMG. "This testing will ultimately decrease the number of amniocenteses, and thus reduce the number of miscarriages caused by amniocenteses. It will also help us identify patients who will need an amniocentesis or CVS where we may have missed them before. A better test that produces fewer false positives and negatives drives better patient care, and that's exciting for the future."

  2. Genetic sonogram improves accuracy of noninvasive prenatal screening and detection of Down's syndrome (The Medical News, Nov, 2009)

    3. The addition of a "genetic sonogram" maximizes the accuracy of non-invasive testing for Down's syndrome, said a Baylor College of Medicine researcher who was lead author of a landmark study in the current issue of Obstetrics and Gynecology.

    A genetic sonogram is simply a sophisticated ultrasound that details the fetal anatomy in the second trimester, looking for the presence of major fetal anomalies or specific anatomic features (so-called 'soft markers') that might be found in a child with Down's syndrome. The detection rate of Down syndrome babies varied from 69 percent for the genetic sonogram alone to as high as 98 percent with certain combinations of the biochemical markers. More importantly, the improved detection rate was accompanied by a decrease in the screening tests false positive rates (or falsely reported risk of Downs syndrome in a normal pregnancy). .

  3. Blood taken from a pregnant woman may reveal if her baby has a wide range of genetic diseases, researchers claim (Euclides.net, Genetica, Nov, 2008)

    4. The discovery that DNA from the unborn child can be found in the mother's plasma - the part of the blood once cells have been removed - opened new possibilities for testing. About 10% to 15% of the DNA in the plasma comes from the baby, and the rest belongs to the mother. Scientists can look for defective DNA sequences passed from the father this way, but it is far more difficult to check for faulty sequences passed on by the mother - as they are identical to the "background noise" - the faulty sequences in the mother's DNA.

    The Hong Kong team may have overcome this, by devising a method to check for minute differences in the amount of faulty DNA carried in the mother's plasma compared to the sample derived from the unborn baby. In a healthy non-pregnant woman carrying the disease, with one normal and one faulty gene, exactly half the DNA sequences will be faulty and half non-faulty, mirroring her genetic makeup.
    If she is pregnant, and the baby also has inherited the same genetic make-up, these proportions will remain the same.

    However, if the child has two copies, and is destined to develop the disease, the numbers of faulty genes in the mixture will be very slightly higher, and by using digital technology to count this, an accurate assessment can be made, say the scientists.

  4. New research raises possibility of prenatal screening for autism
    5. (Health News, Telegraph.co.uk, Jan, 2009)
    Scientists at Cambridge University discovered that high level of testosterone in the amniotic fluid of pregnant mothers was linked to autistic traits in their children. The findings raise the possibility of undertaking tests in the womb to detect the condition, which would allow parents the controversial ability to decide whether to terminate foetuses.

    Experts from the university's autism research centre discovered the testosterone link after studying 235 children from birth to the age of eight. They found that when high levels of the hormone were found, children showed autistic traits such as a lack of sociability and verbal skills by the time they were eight.

  5. Integration of genetic counselling and prenatal testing within the health system of Arab countries (The Dubai Declaration, 2nd Pan Arab Human Genetics Conference, Nov, 2007)
    6. The 2nd Pan Arab Human Genetics Conference, which convened on 20 - 22 November 2007 in Dubai, crowned this vision by the organization of a Public Forum on "The Ethical Perspectives of Human Genetic Applications in the Arab World". Due to the dramatic spread of genetic disorders in the Arab World, the conference faculty encourages the integration of genetic counseling and prenatal testing within the health system of Arab countries, while taking into account the moral imperatives and legal controls regarding the confidentiality of information. They also noted the importance of preimplantation genetic diagnostic techniques that are psychologically, religiously, and socially acceptable.

    The conference faculty recognized the spectacular progress of medicine in the modern era, which has led to the discovery of new cases of congenital abnormalities and genetic disorders prenatally, not considered by Islamic jurisprudence academies and authorities so far. They pointed out that many of these cases cause premature deaths or the birth of children suffering from severe chronic diseases that are incompatible with normal life. They, therefore, request the scientists specializing in juristic sciences to be diligent and interpret and define new cases for which abortion could be conducted.

    The conference faculty also recommended the popularization of genetic sciences as a major step towards limiting the spread of genetic disorders in the region.

  6. Parents' attitudes to different genetic disorders in Saudi Arabia (Genetic Testing in Saudi Arabia Project, King Faisal Specialist Hospital & Research Centre, 2008)
    Saudi parents are favorably inclined towards prenatal diagnosis and there is a strong correlation between parents' attitudes toward prenatal diagnosis and termination of the pregnancy in a range of diseases. However, parents have different attitudes towards prenatal diagnosis and termination of the pregnancy between conditions; this finding suggests that parents' perceive the genetic condition differently according to their individual experience. Hence, a great deal of knowledge about parents' culture and experience and a large range of powerful strategies for attacking parents' problems through proper counseling, would encourage development of more effective ways of addressing problems such as the effect of the disabled child on other family members' marriage prospects. Also, it was apparent that the kind of participants (e.g. with or without an affected child) and parents' individual experience both play a critical part within and between countries in influencing attitudes toward prenatal diagnosis and termination of pregnancy. New technologies provide parents with more reproductive choices but also present them with more dilemmas because of the choices they have to make and religious opinion about their choices- according to a study conducted by King Faisal Specialist Hospital and Research Centre.
Pre Marital Screening