Continuous Research and Development into DNA Molecular Diagnostic Methods
What are the risks of diabetes in pregnancy?
Diabetes is a common health problem. Women with diabetes have increased risk of having problems or complications in pregnancy. The risk also depends on how long diabetes has been present and if there are complications such as high blood pressures and kidney damage. Women with poorly controlled diabetes in early pregnancy have a two to four times increased risk of a birth defect in the baby such as heart defects and neural tube defects. In the later part of preganncy, there
is an increased risk of having a large baby (macrosomia) that may necessisate a Caesarean delivery. Stillbirths tend to be more common and pre-eclampsia risk is increased.
The baby’s lungs mature more slowly and newborns of diabetic women have increased risk of respiratory distress syndrome, hypoglycaemia (low blood sugar), low calcium and high bilirubin levels in the blood. These substances are routinely measured in babies of diabetic mother. (Bilirubin is the waste product that results from the breakdown of haemoglobin molecules from worn out red blood cells. It is excreted from the body as the main component of bile. Excessive levels of bilirubin turn the skin yellow. Very high levels of bilirubin in the bloodstream can cause permanent brain damage in newborn infants.)
Effects of Diabetes on the Mother:
- High blood pressure, pre-eclampsia.
- Worsening kidney damage.
-
Worsening retinopathy (eye damage).
- Urinary tract and other infections.
- Polyhydramnions (increased liquor).
- Malpresentation, premature labour (increased possibility).
- Instrumental delivery (increased possibility).
- Caesarean births (increased possibility).
Effects of Diabetes on the Baby:
- Macrosomia (big baby).
- Growth restriction (problems with growth).
- Birth defects.
- Stillbirths.
- Respiratory distress syndrome.
- Glucose (lower level).
- Calcium (lower level).
- Bilirubin (higher level).
- 2% risk of diabetes by age 20 if only mother has diabetes; 5% if father alone has diabetes.
Based on Is My Pregnancy Normal?, Dr.Patrick Chia & Dr. S. Raman, 2005, Discern Publishing House Sdn. Bhd.
What is the nuchal translucency screening test?
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
- 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
What are the diagnostic prenatal tests?
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.
First Month of Pregnancy
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.
If PYELECTASIS is confirmed, would the FUTURE PREGNANCY be affected too?
An FA Scan is essential to further assess the other organs of the affected baby to look for other soft markers and malformation. The more soft markers there are, the higher the risk of chromosomal abnormalities would be. These expecting mothers, especially those older than 36 years of age, would be recommended to undergo amniocentesis (aspiration of the amniotic fluid) to confirm the baby’s chromosomes. If the baby’s chromosomes are confirmed to be normal, then, pyelectasis may also be the very early beginning of urinary tract problems. Then, serial ultrasound scans would be needed to monitor the progress of this dilatation.
If this baby is affected by Down Syndrome, the next pregnancy theoretically should be at higher risk as the mother is getting older. However, it may not always be so. Thus, all future pregnancies should have prenatal testing to confirm the baby’s chromosome. If this pyelectasis baby is normal chromosomally, then the recurrence risk is 6 times in all future pregnancies. Overall, 3% of all chromosomally and structurally normal babies have transient pyelectasis. The dilatation would resolve by itself before birth.
From: Parenthood Magazine May 2008
PYELECTASIS!!! Is Your Unborn Baby At Risk?
Do you know that pyelectasis (Renal Pelvis Dilatation) is an abnormality that could be found in a baby while she is still residing in her mummy’s womb? It is the dilatation of the renal pelvis, or the part of the kidney from where the urine pipe (ureter) starts. It signifies the soft marker of chromosomal abnormalities. Chromosomes determine the genetic makeup of an individual. Soft marker is something which alerts the doctor of possibility of chromosomal problems in the baby. If a baby is diagnosed to have pyelectasis, she has 1.6 times higher chance of having Down Syndrome. The more soft markers are detected in the baby, the higher the risk of Down Syndrome would be.
If the pregnant mother whose baby has pyelectasis is 36 years or older, the baby she carries has 2.2% chance of being Down Syndrome. If the expecting mother is younger than 36 years old, then the chance of her baby being Down Syndrome is only 0.33%. Thus, older expecting mothers would be recommended to undergo amniocentesis (aspiration of the amniotic fluid) to confirm the baby’s chromosomes. Normally is it found on Foetal Anomaly Scan (FA Scan) done between 18 and 23 weeks to check the normality of the baby’s different organs. However, if FA Scan is not performed, it may be just by chance during the routine ultrasound scanning that it is detected.
If the pelvic dilatation is between 4 and 7 mm, it is considered mild. 80% of such cases would resolve by itself before birth. 17% may only resolve to normal after birth and 3% of cases would need long term follow-up. If the dilatation is more than 7 mm, then only 44% may resolve, usually after birth. The rest may have urinary problems like obstruction or reflux (back flow of urine upwards). These cases would need to be further assessed after birth with ultrasound scan, as well as a voiding cystourethrogram, a test used to visualise the urethra and urinary bladder that takes place during micturition (voiding).
From: Parenthood Magazine May 2008
Checking for Down's syndrome in pregnancy
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
How would i know which test are necessary for me? How can i decide?
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:
-
Family history of genetic condition or you know you are a carrier
of a particular condition such as Thalassaemia. -
Exposure to a serious infection during pregnancy such as rubella or
toxoplasmosis. -
Exposure to a harmful substance that can cause a birth defect.
-
A previous unsuccessful pregnancy or a child with a birth defect.
-
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.
Aneuploidy in humans causes abnormal phenotypes
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
Fourth Month of Pregnancy (16 weeks)
During this period of time, the baby’s face is starting to look more human. His/Her eye moving closer together, toes and finger clearly seperated, eyelids, eyebrows, eyelashes, nails and hair are formed. Teeth and bones become denser. The intestine will also shifting into their proper place. Ear shifting from the neck to the side of the head. Your baby can even suck his or her thumb, yawn, stretch and make faces.
The nervous and muscle system is starting to function. He/She beginning to respond to outside stimuli. If mommy’s abdomen is poked, the fetus will try to wriggle away. The reproductive organs and genitalia are now fully developed and you may know your baby’s sex; boy or a girl by using ultrasound. The baby’s heartbeat may now be audible through an instrument called a Doppler.
From http://www.webmd.com/solutions/sc/pregnancy-week-by-week/weeks13-16