What is microdeletion syndrome?
Microdeletion syndromes are a group of rare genetic disorders caused by the loss of a small piece of genetic material from a chromosome. These deletions are usually too small to be seen under a microscope and can occur spontaneously or be inherited from a parent who carries the deletion.

What causes microdeletion syndromes?
Throughout your life, your cells replicate by dividing — and in the process, your body split up DNA strands to make them more manageable to use. But once in a while, a tiny bit of a chromosome is removed during this process, resulting in a microdeletion.
The effect a microdeletion has on your baby’s health and development depends on its location and size. Some microdeletions can cause intellectual disability, problems with motor skills or miscarriage, while others do no damage at all
There are many types of microdeletion syndromes, each with its own set of symptoms and associated genetic deletions. Some of the most well-known microdeletion syndromes include:

1. Williams syndrome: caused by a deletion of genetic material on chromosome 7, Williams syndrome is characterized by a distinctive facial appearance, intellectual disability, cardiovascular problems, and a friendly personality.
2. DiGeorge syndrome: caused by a deletion on chromosome 22, DiGeorge syndrome is associated with congenital heart defects, cleft palate, immune system deficiencies, and developmental delays.
3. Prader-Willi syndrome: caused by a deletion on chromosome 15, Prader-Willi syndrome is characterized by intellectual disability, low muscle tone, and an insatiable appetite that can lead to obesity.
4. Angelman syndrome: also caused by a deletion on chromosome 15, Angelman syndrome is associated with intellectual disability, developmental delays, seizures, and a happy, excitable demeanor.

How common are microdeletions?
Unlike chromosomal abnormalities, which are more likely to occur in women with risk factors (such as age 35 years or older or with family history of a genetic disorder), microdeletions seem to occur randomly (which means they don’t usually run in families) and equally affect all pregnancy regardless of risk factors. 
In fact, some estimate nearly all of us have some microdeletion in our chromosomes. This condition may be underdiagnosed, which means it could occur more frequently.

What does it mean if I get a positive result?
Expanded NIPT can be used to detect  microdeletion, this is not a diagnostic test, and can’t tell you with 100 percent accuracy, it only tells you how high the risk is. If it’s high, you may need further diagnostic testing, such as CVS and amniocentesis with microarray testing which are invasive tests with a very small risk of infection and miscarriage.
Knowing in advance can prepare you to take steps to improve baby health and quality of life. While there is no cure, a variety of therapies are available. Once the baby is born, you can work with medical specialists for a thorough evaluation to treat cardiac, neurological, palate, bone, immune, hearing or vision problems etc. 

E.g. Babies with 22q deletion syndrome have problems  maintaining calcium in their bodies — knowing this earlier informed doctors they need to monitor these levels from birth and treat them when necessary. 

Knowing your baby has a microdeletion might seem scary, but most parents find it empowering, as it allows them time to prepare and assure the best and safest outcomes.
Some parents may feel anxious and worried before getting tests like NIPT, CVS and amniocentesis. If this is the case for you, consider talking to a doctor about what positive test results could mean for your baby.