So you were told you’re of advanced maternal age in pregnancy, not cool, right? Why is it so problematic that you decided to focus on your career, then your family? Or maybe it took you longer to get pregnant than you anticipated. Or, let’s face it, accidents happen. Why would being over 35 years old and pregnant be such a big deal?
To help answer this question, let’s review some background information. Since Down syndrome is the most common chromosome disorder seen at birth, we’ll use it as an example. Down syndrome is a genetic condition associated with intellectual disability and birth defects due to an extra chromosome. Chromosomes are the containers for all of our genes in our cells. Therefore, if a person has an extra chromosome, they have extra genes, which could cause a variety of developmental problems. Since Down syndrome is a chromosome problem, it is considered a genetic condition, but it is not typically inherited. In fact, 95% of cases of Down syndrome happen sporadically, when an extra chromosome is present in the reproductive cells (eggs and sperm) that make that one pregnancy. That means, there is a chance of Down syndrome in every pregnancy and parents do not cause it to happen. Further, your family history may not impact your risk of having a child with Down syndrome.
If chromosome problems, like Down syndrome, are mostly due to sporadic changes in reproductive cells, why am I getting picked on about my age in pregnancy? Women are actually born with all the eggs they will ever have, so when they are 35 years old or older, so are their eggs. Research has shown that older eggs are more likely to have sporadic chromosomal changes that could lead to Down syndrome (or other chromosome problems). So, to continue with our example, the chance to have a baby with Down syndrome at 35 years old is 1 in almost 400, whereas the risk for a 40 year old is about 1 in 100. Men are not born with all of their reproductive cells, but sporadic chromosome changes do occur in sperm too, just not as often as they do in eggs.
Now you may be thinking to yourself, that 1 in 100 is 1%, so 1 in 400 is actually less than that and you’d be right! So why did medical practitioners decide that the cutoff for advanced maternal age in pregnancy is 35 years old? As some of you may know, amniocentesis is an invasive procedure available in pregnancy to diagnosis chromosome problems like Down syndrome (among other things). While this procedure is valuable for some families, it is associated with some risk, including miscarriage or infection. More precisely, the risk for a complication from amniocentesis is about 1 in 400. Now where have I heard that number before…. oh that’s right, that’s the risk of Down syndrome for a 35 year old. It all makes sense now, if the risk of Down syndrome is the same as the chance for a complication from a procedure that could diagnose it, that’s when more testing should be offered.
The bottom line is that since chromosome problems, like Down syndrome, can occur in any pregnancy, all women are offered genetic screening to learn about their specific risks. If a woman is older than 35, and therefore at more risk, she is offered more genetic test options. Options being the key word though, because you’ll always get to decide, which, if any genetic tests, you wish to pursue in pregnancy. You’ll have access to genetic counselors, doctors, and advanced practice nurses, who can all help you decide what’s right for your family.
– Michelle Maxedon, GCC