We have discussed Down's syndrome at length; what are the other chromosomal disorders?
There are several chromosomal disorders but Down's syndrome affects one in 700 newborns. However, this figure is fluid and, in the medium- and long-term, is bound to be affected by changes in pregnancy patterns (the proportion of women having babies in their "later" years) and the accuracy of screening tests.
Other less common conditions are Edward's syndrome (Trisomy 18); Patau's syndrome (Trisomy 13), Turner's syndrome (XO) and Klinefelter's syndrome (XXY). We shall discuss each one them briefly below.
Edward's syndrome diagnosis
What about Edward's syndrome?
This is a chromosomal disorder where there is an extra chromosome on pair number 18; hence it is called "Trisomy 18". It is characterized by a variety of severe physical and organic defects. The baby may die in the womb or could be delivered alive, only to die a few weeks later. It is virtually unknown for an Edward's syndrome baby to survive beyond twelve months. The active advice, when the diagnosis is made during pregnancy, is to terminate the pregnancy. The final decision, of course, rests with the mother.
Is risk of Edward's syndrome associated in any way with maternal age?
Yes. As with Down's, the risk increases with advancing maternal age. At twenty, the risk is estimated at around 1 in 3600; twenty years later, the risk has shot up to 1 in 200, an eighteen-fold increase. There is no association with paternal age.
Can the screening tests used for Down's help to detect Edward's syndrome?
Absolutely. The hormones are variably affected in this condition as well, so suspicion could be triggered following a "double" or "triple" test. Even if this does not arouse suspicion, the detailed anatomy scan at 18-20 weeks (which virtually every expectant mother gets as part of routine care) will almost certainly do so. This is because the physical and organic defects associated with the condition are almost always there and relatively easy to detect. An invasive test will be needed to confirm the diagnosis.
Can an Edward's syndrome (Trisomy 18) baby survive into later childhood or even adulthood?