Continuous Research and Development into DNA Molecular Diagnostic Methods
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.
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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.
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