This prenatal test (also called the NT or nuchal fold scan) can help your healthcare practitioner assess your baby’s risk of having Down syndrome (DS) and some other chromosomal abnormalities as well as major congenital heart problems.

The NT test uses ultrasound to measure the clear (translucent) space in the tissue at the back of your developing baby’s neck. Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average.

The NT scan must be done when you’re between 11 and 14 weeks pregnant. (The last day you can have it done is the day youturn 13 weeks and 6 das pregnant). It’s usually offered along with a blood test in what’s known as first trimester combined sreening.

Like other screening tests, an NT scan won’t give you a diagnosis. But it can assess your baby’s risk for certain problems and help you decide whether you want to have chorionic villous smpling (CVS) or amniocentesis to find out whether your baby is actually affected.

The NT scan has been performed in the United States since 1995, mostly at large medical centers. Ultrasound technicians (sonographers) and doctors need special training and high-resolution ultrasound equipment to perform it correctly. They must be certified by the Fetal Medicine Foundation in London, the organization that sets the international standards and provides the software that enables a doctor to evaluate your baby’s risk. Therefore the nuchal scan will provide the following information:

• Accurate assessment of gestational age and hence verifying the expected date of delivery.

• Assessment of the risk of Down’s Syndrome by NT measurement and the presence or absence of the nasal bone.

• Detection of certain major foetal abnormlities.

• Foetal viability - About 3 per cent of pregnancies fail to carry on when scanned during this time. The diagnosis is made when no foetal heart movement is seen on ultrasound scan.

• Determine the number of foetuses as multiple pregnancies need closer monitoring.

http://www.babycenter.com/0_nuchal-translucency-screening_118.bc

The diagnostic tests in the prenatal period are specialized tests such as amniocentesis, chorionic villous sampling (CVS) and foetal blood sampling (FBS) which are able to detect foetal abnormalities especially chromosomal abnormalities such as Down’s Syndrome. Where a genetic disorder is known, such as in Thalasemia (an inherited blood disorder), a gene probe for the defect is used to test for the condition in the baby.

Since these tests are “invasive”, i.e. they involve sampling with a needle or small cannula (tubing), there is a procedure-related risk of miscarriage between 0.5 and 1.0 per cent.

Amniocentesis

This is the commonest of the three specialized tests and involves drawing some amniotic fluid that surrounds the baby for analysis. This test is done under ultrasound guidance, using a long, narrow needle. It can be performed from 15 weeks onwards. The results usually take about 8-10 days to be ready. The risk of miscarriage is 0.5 per cent, over and above the normal risk of miscarriage. Amniocentesis is commonly performed to check for chromosomal abnormalities in women over the age of 35, those with positive triple test or when an abnormality is found on ultrasound scan.

Chorionic Villous Sampling (CVS)

Chorionic villous sampling is essentially a biopsy, where a piece of tissue is taken from the placenta. This can be done earlier, usually from 10-12 weeks of pregnancy. Placental tissue contains cells, which are similar genetically to the baby, is sent for analysis. Depending on where the placenta is situated, CVS can either be done through the trans-abdominal or trans-cervical (through the neck of the womb) route. It is associated with a slightly higher risk of miscarriage, between 0.5 and 1.0 per cent, and can be done earlier compared to an amniocentesis. Women with increased risk of chromosomal abnormalities (those above 35 years of age) and genetic diseases (such as ?- and ß-Thalassaemia) may be offered a CVS.

Based on Dr. Patrick Chia & Dr. S. Raman, Is My Pregnancy Normal?, Discern Publishing House, 2005.

During your first month of pregnancy (4 weeks)

      1                         2                    3                        4                         5

1) Ovulation Occurs

The time is right; now you just need this egg to be fertilized! Did you know that during your

pregnancy that your uterus will increase its capacity by 1000 times?

2) Gender Determined

Immediately upon fertilization your little one is set as a boy or a girl. Ladies, this is one that you can’t

take credit for since it is up to the sperm to determine the sex of your baby. Sperm carries

either a “X” (girl) chromosome or a “Y” (boy) chromosome.

3) Implantation

Implantation bleeding (spotting) may occur about 10 - 14 days after conception. You may believe you are starting

your period but generally this bleeding is extremely light and lasts only day or so.

4) Neutral tube forms

It will develop into the nervous system (Brain, spinal cord, hair and skin). Already your baby has the foundation for

though, sense, feeling and more!

5) Heart and primitive circulatory system form

While still in its beginning stages, this is the very life support system that will carry your child throughout his or her

life.

The prospect of having a baby with Down syndrome cause considerable anxiety among women, particularly those over the age of 35. There are tests available to check for this type of fetal abnormality, but they are carried out late in the pregnancy and also carry with them the risk of a possible miscarriage.

However, improvements in ultrasound and blood tests now mean that women can have effective for Down syndrome carried out earlier in the pregnancy and without any possible risks of miscarriage being induced by the test.

A major new study headed by an Irish consultant has shown that over 95% of Down syndrome cases can now be detected in early pregnancy. Results of the study published in the New England Journal of Medicine demonstrate that new ultrasound and blood tests are now widely available that can detect over 95% of cases of Down syndrome as early as 10 to 12 weeks into a pregnancy.

Over 38,000 pregnant women were provided with a range of ultrasound and blood screening tests at 10 to 13 weeks and then at 15 to 18 weeks gestation. The study found that screening in the first three months of a pregnancy provided a detection rate of Down syndrome of up to 87%, and that other combinations of screening produced a detection rate of 96%.

Traditional tests for Down syndrome, chorionic villus sampling or amniocentesis, both carry a small risk of miscarriage. Women who are interested in the reassurance that these tests provide should be asking their doctors or midwives for early access to combined ultrasound and blood tests. There are technical challenges for health professionals in performing the special ultrasounds involved properly, as measurements that are off by even a fraction of a millimetre can give very inaccurate results.

For further reading go to http://medmediacampaign.com

Some prenatal tests are performed routinely while others are done when there is need for the test. Some of the tests are not without its risks such as an amniocentesis where there is risk of miscarriage. Often the decision to have a prenatal test is a personal one but it is important to gather all the correct information so that an informed decision can be made.

You may wish to consider a prenatal test in the following:

1. Family history of genetic condition or you know you are a carrier 
   of a  particular condition such as Thalassaemia.

2. Exposure to a serious infection during pregnancy such as rubella or
   toxoplasmosis.

3. Exposure to a harmful substance that can cause a birth defect.

4. A previous unsuccessful pregnancy or a child with a birth defect.

5. Anxious to know if your baby has a detectable abnormality.

Based on Dr. Patrick Chia & Dr. S. Raman, Is My Pregnancy Normal?,
Discern Publishing House, 2005.

Geneticists are so interested in aneuploidy because its relationship to certain inherited disorders in humans. Even though most people are born with a normal number of chromosomes, alterations in chromosome number occur fairly frequently during gamete formation. About 5-10% of all fertilized human eggs result in an embryo with an abnormality in chromosome number. In most cases, these abnormal embryos do not develop properly and result in a spontaneous abortion very early pregnancy. Approximately 50% of all spontaneous abortions are due to alterations in chromosome number.

In some cases, an abnormality in chromosome number produces an offspring that can survive. Several human disorders involve abnormalities in chromosome number. The most common are trisomies of chromosomes 21, 18 or 13, or abnormalities in the number of the sex chromosomes. Most of the known trisomies involve chromosomes that are relatively small. Trisomies of the other human autosomes and monosomies of the autosomes usually produce a lethal phenotype that causes early spontaneous abortion.

Some human abnormalities in chromosome number are influenced by the age of the parents. Older parents are more likely to produce children with abnormalities in chromosome number. For example, the incidence of Down Syndrome rises with the age of the parents, particularly that of the mother. This syndrome was first described by the English physician John Landdon Down in 1866. This association between maternal age and Down Syndrome was later discovered by L.S. Penrose in 1933, even before the chromosomal basis for the disorder was identified by the French scientist Jerome Lejeune in 1959. Down Syndrome is most commonly caused by nondisjunction at meiosis I in the oocyte.

From www.awl.com/bc

The human immunodeficiency virus (HIV), or sometimes referred to as AIDS virus, attacks the body’s immune system and render it too weak to cope with infection and certain tumours. The latter stage when this happens is called AIDS (acquired immune deficiency syndrome). The progression to full-blown AIDS can now be controlled with modern-day antiviral therapy. HIV is acquired through sex and through blood such as when needled are shared between intravenous drug abuser.

  

Being HIV positive has tremendous implications to both the mother and her baby. HIV does     not usually worsen in pregnancy. There is no evidence of pregnancy increasing the risk of progression of the disease. However, women with HIV tend to have an increased risk of miscarriage, intra-uterine growth restriction, premature births and low birth-weight babies. These complications reflect more on the mother’s state of health rather than the virus itself. The current antiviral treatment does not appear to cause any foetal abnormalities

Many issues need to be considered in an HIV positive woman who is pregnant. Combined care with an HIV expert is essential to reduce the risk to both the mother and her baby.

Based on the New York Heart Association’s classification