Multiple congenital defects can be caused by various factors which are not necessarily genetic. However, there are more than seven thousand known genetic syndromes characterized by a combination of birth defects. In some of these syndromes, symptoms include intellectual disability, while in other syndromes birth defects are mostly structural (related to the structure of various body parts).
In some cases, an initial anomaly occurs and causes subsequent anomalies. However, in many cases (and in fact in most syndromes), the birth anomalies are developed simultaneously and result from the same genetic mutation, or several common mutations.
Environmental causes of multiple congenital anomalies
One of the factors that may cause multiple congenital anomalies is the use of certain kinds of medication during pregnancy, which can harm normal fetal development.
In addition, multiple anomalies can occur due to mechanical pressure on the fetus. Such pressure can occur in a multiple pregnancy (twin or triplet pregnancy), due to myomas (tumors in the uterus), or other reasons. Additional factors can include exposure to radiation during pregnancy, exposure to various infections during pregnancy, and more.
Moreover, additional environmental factors that can cause multiple birth anomalies include defects in fetal circulation in which the fetus does not receive a sufficient supply of blood during critical stages of organ development.
Circulation abnormalities can cause an incomplete development of an organ or tissue but can also cause the destruction of an organ after its development, as well as non-development of that organ.
This article will not discuss the various environmental factors, but rather the genetic factors that can cause multiple congenital anomalies.
Diagnosis – can these anomalies be diagnosed prenatally?
Not all defects can be diagnosed during pregnancy, but many can be detected during a simple ultrasound scan. Whenever multiple anomalies are detected, further inquiry, which includes different additional tests, is required.
Amniocentesis is often recommended to rule out or confirm the existence of various chromosome abnormalities. A comprehensive examination is also required for diagnosing multiple anomalies.
Experts recommend counselling at a multidisciplinary clinic that includes specialists that can interpret findings in ultrasound scans, a geneticist, a neonatologist, and other healthcare professionals.
What are common congenital anomalies?
Here are common anomalies that can appear as an isolated finding, or as part of a syndrome characterized by several simultaneous anomalies:
- Heart defects – congenital heart defects are relatively common; the most common heart defects are atrial septal defects and atrioventricular septal defects.
- Gastrointestinal defects – since the development of the gastrointestinal tract is considered particularly complex, this is therefore one of the most common organ systems to suffer damage during fetal development. Common anomalies include gastroschisis (a condition in which the intestines exit the body), trachea – esophageal fistulas, and more.
- Orofacial clefts – anomalies in the facial and oral area can occur in many cases without the involvement of other organ systems. The most common are a cleft palate and cleft lip. However, whenever these malformations are diagnosed, a comprehensive examination for detecting other possible anomalies.
- Anomalies of the nervous system – congenital anomalies of the central nervous system can be severe and result in perinatal mortality but can also be milder and cause partial or full paralysis, mental health conditions, behavioral disorders, seizures, and more.
Can genetic screening rule out multiple congenital anomalies?
Various prenatal screening tests are available to couples interested in having a child who are at risk for diseases characterized in multiple congenital anomalies. In addition, couples at high risk can choose to undergo pre-implantation genetic diagnosis (PGD), to prevent the fetus from developing these conditions.
Not all known syndromes can currently be tested. However, the more genes are interpreted, and the more gene mutations are detected, more screening tests can become available.
Although some screening tests are not routinely performed, parents-to-be can turn to private genetic institutes and undergo these tests when needed, especially in families with a family history of certain genetic inherited disorders.