Congenital Anomalies

Congenital anomalies is the term used to describe birth defects, abnormalities, or malfunctions that are present at birth.^(1,2)  Congenital anomalies can be structural (such as structural health defects), or functional (such as metabolic disorders) in nature.⁽³⁾  Anomalies may be present from the time of conception, but mainly occur during the embryonic period (the time from conception to the end of the seventh week of gestation), or the early fetal period (eighth to sixteenth week of gestation).  It should be noted that some congenital anomalies may not be diagnosed until months or years after birth. 

In Canada, approximately 1 in 25 babies are diagnosed with one or more congenital anomaly every year.⁽²⁾  The Canadian Congenital Anomalies Surveillance System (CCASS) estimates that the frequency of congenital anomalies in recent years is about 3-5% of total births.⁽¹⁾ In Canada (excluding Quebec) in 2010, the prevalence of congenital anomalies was 397 (390-405) per 10,000 total births.  This represents a slight increase in prevalence from 377 (370-384) per 10,000 birth in 2007, but a decrease from 460 (452-468) per 10,000 births in 2001.⁽²⁾ 

Children can be born with multiple congenital anomalies that can range from mild, to severe, to life threatening.  Infants born with severe anomalies (e.g., anencephaly, trisomy 13, trisomy 18, or inoperable congenital heart defects) often die.⁽⁴⁾  Congenital anomalies are the second leading cause of neonatal death⁽²⁾ and it is estimated that about 4000 newborns per year in Ontario will require extended specialized long-term care due to the presence of a congenital anomaly.⁽⁵⁾  There has been a decline in infants deaths due to congenital anomalies in Canada from 1998 to 2010, suggesting that increases in prenatal diagnosis and pregnancy termination have increased in recent years.^(1,6) Not all congenital anomalies are serious, however, and many can be treated.

About half of all congenital anomalies cannot be linked to a specific cause, but there are some known risk factors:⁽³⁾ 

• Socioeconomic factors: anomalies tend to be higher in underdeveloped countries, possibly due to the fact that those mothers are more susceptible to malnutrition, or increased exposure to other risk factors, such as infection or alcohol.⁽³⁾  Advanced maternal age is another known risk factor, such as in the case of Down Syndrome.
• Genetic Factors: some ethnic groups have a relatively high prevalence of rare genetic mutations that can lead to higher risk of congenital anomalies.⁽³⁾
• Infections: Infections such as syphilis and rubella can cause birth defects, particularly in underdeveloped countries.⁽³⁾
• Maternal nutritional status: Obesity, diabetes mellitus, iodine deficiency and folate insufficiency are all linked to increased likelihood of congenital anomalies.⁽³⁾
• Environmental factors: maternal exposure to alcohol, tobacco, pesticides, medications and radiation may all increase the risk of congenital anomalies.⁽³⁾

There are some preventive measures that may help to decrease the likelihood of congenital anomalies:

• improving maternal nutritional status,⁽³⁾
• ensuring adequate vitamin and mineral intake,⁽³⁾
• ensuring healthy pre-pregnancy and pregnancy weights,⁽³⁾
• controlling pre-conceptional and gestational diabetes,⁽³⁾
• avoiding or abstaining from the intake of harmful substances such as alcohol or tobacco,⁽³⁾
• increasing vaccine coverage,⁽³⁾ and,
• limiting exposure to hazardous environmental exposures.⁽³⁾

Common Severe Congenital Anomalies

Congenital heart defects (CHDs) are the most common type of severe congenital anomaly.  Other common severe anomalies include Down syndrome, neural tube defects and orofacial clefts.

Congenital heart defects are the most common type of severe congenital anomaly and are an important cause of morbidity and mortality among infants.⁽¹⁾ They include abnormalities of the heart and vessels that are of functional significance and have genetic and non-genetic risk factors.  Some of the modifiable risk factors include maternal rubella during pregnancy, multi-vitamin/folic acid supplementation, medications, diabetes mellitus and maternal phenylketonuria.  The prevalence of CHDs are 98.9 per 10,000 total birth in Ontario (2000 to 2009).⁽¹⁾

Down Syndrome (DS) occurs in 1 in 800 births, and is characterized by the presence of an extra 21 chromosome which causes intellectual delay, a well-defined facial appearance, and a number of other major and minor congenital anomalies, such as heart defects and digestive abnormalities.^(1,7)  Congenital heart defects and respiratory infections are a common cause of death in children and young adults with DS. The most established risk factors are advanced maternal age and family history. The birth prevalence of DS in Ontario is about 124 per 10,000 total births (1998 to 2007).⁽¹⁾

Neural tube defects (NTDs) such as spina bifida, anencephaly and encephalocele, are a group of anomalies of the central nervous system caused by defective closure of neural tube during the development of the embryo.⁽¹⁾ Most defects are due to multifactorial inheritance, that is, the interaction between genetic and environmental factors.  Inadequate intake of folic acid is the best established risk factor for NTDs and remains an important modifiable risk factor in Canada. In Ontario, the neural tube defect rate is 4.0 defects per 10,000 total births (2001 to 2007).⁽¹⁾

Orofacial clefts - Every year about 600 babies in Canada are born with orofacial clefts (OFCs).⁽²⁾  These defects form when the infant's lip or mouth do not form properly during pregnancy.⁽⁸⁾  An infant can have a cleft lip, a cleft palate, or both.  The causes for these defects remain largely unknown and thus, these anomalies continue to pose challenges in terms of health care.  The OFC birth prevalence in Ontario is 14.6 per 10,000 total births, which is slightly lower than the national prevalence of 16.3 per 10,000 total births.

Figure 1.  Prevalence of congenital anomalies in KFL&A, 2012-2013¹²

Figure 1 outlines the prevalence of certain congenital anomalies in KFL&A. In addition to some of the anomalies listed above, the figure includes rates on other types of congenital anomalies; musculoskeletal anomalies and genitourinary tract anomalies (see below for definitions). In KFL&A, congenital anomalies occur at a rate of 218.6 births per 10,000 total births.  Congenital heart defects are the most common congenital with a rate of 57.4 births per 10,000 births.  Many types of congenital anomalies occur in very small numbers with rates too small to be reported in Figure 1.

Musculoskeletal anomalies are disorders of the musculoskeletal system present at birth. They can be due to deformity or malformation. Birth defects can occur in any bone or muscle, although the bones and muscles of the skull, face, spine, hips, legs, and feet are affected most often.⁽⁹⁾  Musculoskeletal anomalies include: limb reductions, congenital dislocation of the hip, clubfoot, polydactyly, macrocephaly, congenital scoliosis, and spina bifida occulta.

Genitourinary tract anomalies are disorders of the genitourinary tract system present at birth due to deformity or malformation.  Congenital anomalies in the urinary tract system can include defects in the kidneys, ureters, bladder or urethra.⁽¹⁰⁾  Genital defects are caused by abnormal levels of sex hormones during fetal development and may cause defects of the external genital organs.⁽¹¹⁾

Folate (natural form found in foods) and folic acid (synthetic form added to foods) are forms of a water-soluble B vitamin.⁽¹³⁾  It is recommended that women who are pregnant or trying to get pregnant take a daily multivitamin containing 0.4mg of folic acid.⁽¹⁴⁾  This may help prevent neural tube defects, such as spina bifida that can occur when the neural tube does not close properly during fetal development. 

Women with an elevated risk of having a baby with a neural tube defect may benefit from a higher level of supplemental folic acid on the advice of a qualified health care provider.⁽¹⁵⁾  This priority group includes women with poor dietary quality, low socio-economic status, those in certain ethics groups whose natural diet does not include a lot of folate, and those who are chronic dieters or women who smoke.

Figure 2. Folic acid supplementation during pregnancy in KFL&A, 2012-2013¹²

Interpretation for Figure 2

About 40% of mothers in KFL&A took a folic acid supplementation both during pre-conception and pregnancy in 2012 & 2013.  Only 10.8% of mothers did not supplement at any time with folic acid. 

Public Health Agency of Canada's Canadian Congenital Anomalies Surveillance System (CCASS) uses hospitalization data from the discharge abstract database (DAD) via the Canadian Institute for Health Information (CIHI) to determine prevalence of congenital anomalies.⁽¹⁾ It should be noted that there are limitations associated with using hospitalization data to determine the prevalence of congenital anomalies among newborns.  First, hospitalization data relies on codes within the International Classification of Diseases 10th Revision (ICD-10,) which are not validated, and can only identify anomalies within the first 30 days after birth due to administration restrictions.

The data is also restricted to live births and stillbirths, does not always have completed information on gestational age, and does not capture anomalies present in terminations of pregnancy before 20 weeks of gestation.  In addition, there is no written description of the individual anomaly provided along with the ICD-10 codes, and thus no verification of the anomaly can be completed.⁽¹⁶⁾ These limitations may mean that the prevalence of congenital anomalies is underestimated.

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2. Canadian Perinatal Surveillance System. Perinatal Health Indicators 2013: A report from the Canadian Perinatal Surveillance System. 2013 [cited 2015 Mar 17]. Available from : http://publications.gc.ca/collections/collection_2014/aspc-phac/HP7-1-2013-eng.pdf
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7. Genetic Home Reference. Down Syndrome. U S National Library of Medicine 2012 [cited 2015 Mar 18] Available from: http://ghr.nlm.nih.gov/condition/down-syndrome
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11. Merck Manual. Genital Defects. Merck Manual [cited 2015 May 1] Available from: http://www.merckmanuals.com/home/children-s-health-issues/birth-defects/genital-defects
12. BORN Information System: Fiscal years 2012 and 2013. [extracted 2017 Jun 13].
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16. Lowry RB. Congenital anomalies surveillance in Canada. Can J Public Health 2008; 99(6):483-485.