Saturday, November 06, 2021

Prenatal Diagnosis and Planning

I've been putting some thoughts into prenatal screening for chromosome anomalies, and what I'd do with potential results. I'm pro-life, so the stereotypical option of "abort anything abnormal" is not appealing to me. But, what plan of action should you have in the case of a prenatal diagnosis if your priority is the optimal outcome for the child? Well, it depends on the specific abnormality found. In my impression, chromosome abnormalities fall into the following categories of outcome:

Probably Insignificant

Examples of this category are sex chromosome trisomies, balanced chromosome rearrangements, and anything that is found to be shared with an asymptomatic parent.

While the child may be at higher risk of certain issues, and XXY and balanced chromosome rearrangements have important reproductive implications for your potential grandchildren, overall, if you hadn't gotten them diagnosed now, there's a decent chance they could have gone their whole life unaware that they have a chromosome anomaly.

In general, I don't recommend doing anything in particular for these anomalies. Most likely, a child with one of these anomalies won't be any different from a chromosomally typical child. If their anomaly has reproductive implications, explain those to them when they reach puberty. And if any symptoms present, treat them as they arise. But don't worry about it, it's not a big deal.

Significant But Not Deadly

Turner Syndrome (monosomy X) and Down Syndrome (trisomy 21) are the two most commonly detected examples of this category. These chromosome anomalies typically have effects that will significantly shape the child's life, and notably increase the risk of life-threatening complications such as heart defects, but the majority of individuals with these conditions do quite well with appropriate treatment. I recommend being ready for the most likely life-threatening birth defects associated with the condition, just in case - for example, make sure your child will have access to a cardiologist if needed at birth. However, you can probably assume that they'll survive, and focus more on planning to help them live their life well.


These anomalies, such as Edwards Syndrome (trisomy 18) and Patau Syndrome (trisomy 13), are very likely to result in your baby's death, before or after birth. For example, 70% of children diagnosed with Edwards Syndrome at 12 weeks gestation will be miscarried or stillborn. Of the liveborn survivors, with aggressive care, about 75% will die before their first birthday.

The good news is that the longer a child survives with one of these conditions, the better their chances are. Most of the life-threatening defects resulting from chromosome anomalies affect the child right from the start. The survivors either get surgical procedures that reduce the severity of their defects, or were lucky enough not to have the defects in the first place. 

Therefore, if they can survive the deadly neonatal period, they're likely to live for many years, even decades potentially. However, the severe ongoing mobility impairment typical of these conditions (which can result in aspiration pneumonia, pressure sores and other immobility-related health issues), as well as the potential for seizures and other slower-acting issues, means that they will likely always be at higher risk of life-threatening health issues than a chromosomally typical person or someone with a milder chromosome anomaly.

For these individuals, if your goal is to maximize survival chances, they need immediate and intensive care if they are lucky enough to be born alive. You will also likely have to fight with doctors who see these anomalies as "lethal" and recommend palliative care rather than trying to keep the child alive. Unfortunately, many doctors don't see these children as worth the immense effort it often takes to keep them alive. This has been shown to be a self-fulfilling prophecy - for example, under palliative care, only 5% of liveborn children with Edwards Syndrome live through their first year, meaning that aggressive care increases their chance of survival five times!


These are the rarer chromosome anomalies, for whom you might only be able to find a few case reports of partially overlapping chromosome anomalies in the research literature.

Their prognosis could be anywhere along the spectrum of the above-listed conditions, and your doctor will probably not know. Unfortunately, many doctors hate to admit that they don't know what to expect, and will instead give you the worst possible outcome as a prediction, so expect to be told a prognosis similar to those typically given for Edwards and Patau Syndrome. Take this with a grain of salt.

My first recommendation is research. The organization Unique has fact sheets on many rare chromosome anomalies, and searching Google scholar can also find you some cases with overlapping affected chromosome regions. If your child has multiple chromosome anomalies (such as an unbalanced translocation causing duplication of one region and deletion of another) and you can only find information for individuals with one or the other anomaly, know that these frequently have an additive effect, with shared symptoms being more severe and potential to experience any non-shared symptoms of either chromosome anomaly. Also, pay attention to breakpoints - if you just look for anomalies in the same broad region, you could end up comparing your child to people whose chromosome anomalies don't actually overlap with theirs. Learn how to read a karyotype - Unique has instructions on this, too. Doctors won't know what to do with your child, so you need to become the expert on their condition.

Secondly, if you can't find good prognosis information, then prepare for the worst, and hope for the best. Be prepared for them to need immediate intensive care at birth, and pleasantly surprised if they don't. Fight to make sure that doctors give them the best treatment possible, knowing that any recommendation of palliative care makes even less sense for these kids than for kids with well-known life-threatening chromosome anomalies. After the neonatal period, prepare for them to potentially be anywhere from totally typically developing to profoundly and multiply disabled, and adjust your expectations as they grow.


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