What are congenital anomalies?
Congenital anomalies are disorders in the morphological, structural or functional development of an organ or system that are present at birth. According to the World Health Organisation (WHO), 500,000 children are born each year with congenital defects in Europe and they are the leading cause of prenatal and perinatal death. Early diagnosis is essential for the survival of these patients and in many cases determines their quality of life.
Aetiology
Approximately half of all children born with birth defects can be identified as having a genetic cause in 25% of cases (chromosomal alterations or gene mutations) or due to environmental causes in 15%.
- Congenital anomalies of genetic origin
The genetic cause of congenital anomalies has been difficult to establish because most of them are characterised by diverse phenotypic manifestations, which in many cases are apparently unrelated and variable for affected individuals. Congenital anomalies of genetic origin may be due to chromosomal alterations, such as Down syndrome, or due to mutations in single genes, such as phenylketonuria or cystic fibrosis.
- Congenital abnormalities due to infectious or environmental factors
Maternal infections during pregnancy are risk factors for the development of malformations in the foetus. Cytomegalovirus infection is associated with sensorineural hearing loss and intellectual disability in newborns and Zika virus infections can result in microcephaly. Furthermore, it is well established that folic acid deficiency during pregnancy increases the risk of having children with neural tube defects or that maternal exposure to certain medications, alcohol, tobacco, psychoactive drugs and radiation during pregnancy may increase the risk of congenital anomalies in the foetus or newborn.
Prevention and diagnosis
Although congenital anomalies occur during embryonic and/or foetal development, not all of them can be detected during the prenatal period and many are diagnosed in the neonatal period or during the first years of life. Their prevention and/or early diagnosis is essential for the correct management and treatment of patients. Preventive actions and/or diagnostic studies can be performed during the preconception, prenatal and/or neonatal stage (Figure).
1. Preconception Stage
- Genetic study of carriers
- Genetic counselling
2. Prenatal Stage
- Healthy lifestyle habits
- Obstetric monitoring
- Genetic diagnosis
3. Perinatal Stage
- Neonatal physical examination
- Newborn screening
- Genetic diagnosis
Preventive measures and diagnostic studies in the preconception, prenatal and perinatal stages.
During the preconception period, genetic studies can be carried out to identify carriers of certain syndromes or anomalies that can be transmitted to the offspring. For families with a previous child born with a congenital defect, a history of repeated miscarriages or consanguineous parents, appropriate genetic counselling is essential to prevent future congenital anomalies. genetic counselling is essential for the prevention of future congenital anomalies in the offspring.
In the prenatal stage, it is essential for women to adopt healthy lifestyles and carry out the established obstetric check-ups. Current ultrasound scans make it possible to detect or establish suspicion of various congenital anomalies such as cardiac alterations, neural tube defects, bone dysplasia or Down's syndrome. Prenatal genetic studies are carried out on samples of amniotic fluid or chorionic microvilli to confirm the diagnosis if these or other foetal abnormalities are suspected.
In the neonatal period, physical examinations of newborns or the screening systems established in the National Health System allow the early detection of many congenital alterations. In the case of a suspected congenital anomaly, tests can be carried out genetic studies genetic studies that include the analysis of the genes associated with the suspected disease or syndrome. Genetic studies allow the diagnosis to be confirmed and the most appropriate treatment to be selected and started early. In addition, obtaining a genetic diagnosis makes it possible to assess the risk of the patient's relatives to suffer from the disease and to initiate lifestyle changes and preventive treatments.
- Word Health Organization
- NEONATAL SCREENING PROGRAMME OF THE NATIONAL HEALTH SYSTEM. EVALUATION REPORT YEAR 2019
- Rojas M, and Walker L. Congenital Malformations: General and Genetic Aspects. International Journal of Morphology. 2012 30(4), 1256-1265. https://dx.doi.org/10.4067/S0717-95022012000400003
- Yinon Y, Farine D, Yudin MH. Screening, diagnosis, and management of cytomegalovirus infection in pregnancy. Obstet Gynecol Surv. 2010 Nov;65(11):736-43. doi: 10.1097/OGX.0b013e31821102b4. PMID: 21375790.
- Cauchemez S, Besnard M, Bompard P, Dub T, Guillemette-Artur P, Eyrolle-Guignot D, Salje H, Van Kerkhove MD, Abadie V, Garel C, Fontanet A, Mallet HP. Association between Zika virus and microcephaly in French Polynesia, 2013-15: a retrospective study. Lancet. 2016 May 21;387(10033):2125-2132. doi: 10.1016/S0140-6736(16)00651-6. Epub 2016 Mar 16. PMID: 26993883; PMCID: PMC4909533.
- Bloom, H. J.; Shaw, G. M.; den Heijer, M. & Finnell, R. H. Neural tube defects and folate: case far from closed. Nat. Rev. Neurosci., 7(9):724-31, 2006.
- Reardon S. Fast genetic sequencing saves newborn lives. Nature. 2014 Oct 2;514(7520):13-4. doi: 10.1038/514013a. PMID: 25279893.
- Meng L, et al. Use of Exome Sequencing for Infants in Intensive Care Units: Ascertainment of Severe Single-Gene Disorders and Effect on Medical Management. JAMA Pediatr. 2017 Dec 4;171(12):e173438. doi: 10.1001/jamapediatrics.2017.3438. Epub 2017 Dec 4. PMID: 28973083; PMCID: PMC6359927.