Health at a Glance
Deaths from congenital anomalies in Canada, 1974 to 2012 Health at a Glance
Deaths from congenital anomalies in Canada, 1974 to 2012

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by Tanya Navaneelan, Caryn Pearson and Teresa Janz

Release date: September 29, 2016

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• Highlights
• Introduction
• Definitions of congenital anomalies examined in this article
• Deaths from congenital anomalies have been decreasing since 1974
• The average age at death from a congenital anomaly has increased in recent decades
• The proportion of infant deaths caused by congenital anomalies has increased
• The infant death rate from congenital anomalies has declined
• Conclusion
• Data sources, methods and definitions
• References and notes
• Related material for this article

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Introduction

Congenital anomalies, commonly referred to as “birth defects”, describe conditions that develop in the fetus at conception or during pregnancy.^{Note 1, Note 2} In Canada, approximately 1 in 25 babies is born with a congenital anomaly annually. While congenital anomalies can be present at the time of conception (e.g., in the case of Down syndrome), they more commonly develop by the end of the seventh week of pregnancy (e.g., in the case of spina bifida), or between the eighth and sixteenth weeks of pregnancy.^{Note 2} There are several hundred separate congenital anomalies, and for the majority the cause is unknown.^{Note 1}

Risk factors for congenital anomalies include: genetics, maternal age, lifestyle factors (e.g., smoking, drinking or using drugs during pregnancy), medication use during pregnancy, maternal chronic diseases (e.g., diabetes, obesity and thyroid disease), and environmental factors (e.g., pollution).^{Note 1, Note 2} Although the vast majority (more than 93%) of infants born with a congenital anomaly survive, in Canada, congenital anomalies are one of the leading causes of infant death (a death before the age of 1).^{Note 1, Note 2, Note 3}

In this article, information on deaths from five congenital anomalies is presented: circulatory system anomalies, spina bifida, and three chromosomal anomalies—Down syndrome, Edwards’ syndrome and Patau’s syndrome. Death from a congenital anomaly refers to all deaths where the underlying cause of death was coded as a congenital anomaly since 1974 according to the International Classification of Diseases (ICD), 8^th, 9^th, and 10^th revisions. Trends in the average age at death and death rates from 1974 to 2012 are presented using data from the Canadian Vital Statistics – Death Database.

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Deaths from congenital anomalies have been decreasing since 1974

In Canada, the age-standardized death rate from all congenital anomalies combined, has been decreasing since 1974, from 53 to 28 deaths per 1,000,000 people in 2012 (Chart 1).  

Looking deeper at specific anomalies, the death rates from circulatory system anomalies and spina bifida have decreased markedly since 1974.

Decreases in deaths from circulatory system anomalies were likely a result of medical advancements. Studies have found that surgery during pregnancy, or shortly after birth, can improve the survival of infants with circulatory system anomalies that affect the heart.^{Note 2, Note 5, Note 6, Note 7}

Decreases in the death rate from spina bifida were also likely a result of early surgical intervention^{Note 6} as well as changes in prenatal care, including folic acid supplementation. It is recommended that women of childbearing age take an additional 0.4 milligrams (mg) of folic acid per day beyond the 0.4 mg recommended for the rest of the population. Furthermore, in 1998, Canada approved the mandatory folic acid fortification of white flour and other selected grains. Since folate deficiency is the most well-established risk factor for spina bifida, both the use of folic acid supplements and the folic acid fortification of some foods have reduced the number of babies born with spina bifida.^{Note 8, Note 9, Note 10}

From 1974 to 2012, the death rate from the chromosomal anomalies studied in this article did not decrease. While the death rate from Edwards’ and Patau’s syndromes^{Note 11} remained relatively stable over this period, the death rate from Down syndrome increased from 2 deaths per 1,000,000 people in 1974 to 5 deaths per 1,000,000 people in 2012 (Chart 1).

The average age at death from a congenital anomaly has increased in recent decades

Most pregnancies and births affected by congenital anomalies do not result in the death of a fetus or an infant.^{Note 1} In Canada, those who are dying from a congenital anomaly are dying at older ages than in previous decades (Chart 2).

In Canada, the average age at death from all congenital anomalies increased by approximately 19 years between 1974 and 2012, from 8 to 27 years of age (Chart 2). This finding can partly be explained by changes in the infant death rate from these anomalies. In 1974, approximately 70% of deaths from all congenital anomalies occurred before the age of 1—this dropped to 42% by 2012 (data not shown).

When specific anomalies were examined, the greatest increase in average age at death was for those who died from Down syndrome. For this syndrome, the average age at death increased by 32 years between 1974 and 2012. This was followed by spina bifida, where the average age at death increased by 26 years, from 2 years to 28 years of age over the same time period (Chart 2).

The average age at death from a circulatory system anomaly was 23 years in 2012 compared with 9 years in 1974.

In contrast, in the case of Edwards’ and Patau’s syndromes, where most infants do not survive past the first year of life, the average age at death has increased very little from 1974 to 2012.

The proportion of infant deaths caused by congenital anomalies has increased

The proportion of all infant deaths, caused by congenital anomalies increased sharply between 1974 and 1981 but has been decreasing gradually since the early-1990s (Chart 3).

The increase in the proportion of infant deaths from congenital anomalies seen between 1974 and 1981, can be partly explained by decreases in other causes of infant death during this time period. The introduction of car seats for children led to fewer deaths from car accidents, and increased vaccine use led to fewer deaths from infectious diseases, just to name a few examples.^{Note 12}

That is, while preventable causes of infant death have been declining (e.g., accidents, death from infectious diseases), many congenital anomalies are not preventable so the proportion of infant deaths from congenital anomalies appears to stay the same or decrease little over the time period studied.^{Note 13} This does not mean there are more deaths from congenital anomalies, it means that relative to other causes, congenital anomalies have become one of the main causes of infant death. In fact, in 2012, congenital anomalies were the leading cause of infant death in Canada, followed by infant immaturity (i.e., short gestation and low birth weight), and complications related to pregnancy.^{Note 14}

Focusing on specific congenital anomalies, the percentage of infant deaths caused by circulatory system anomalies and spina bifida decreased between 1974 and 2012, while the percentage of infant deaths caused by Down syndrome increased. There was no change in the percentage of infant deaths caused by Edwards’ and Patau’s syndromes between 1974 and 2012. Together these two syndromes (Edwards’ and Patau’s) accounted for less than 3% of all infant deaths during this time period.

The infant death rate from congenital anomalies has declined

Overall, infant deaths declined in Canada from 15.0 deaths per 1,000 births in 1974 to 4.8 deaths per 1,000 births in 2012 (data not shown). Similarly, the infant death rate from all congenital anomalies has declined from 3.0 deaths per 1,000 births in 1974 to 1.1 deaths per 1,000 births in 2012 (Chart 4).

The decline in infant deaths from all congenital anomalies has been influenced by various factors, including: increased access to, and use of, prenatal screening; improved prenatal care; termination of pregnancies affected by major anomalies; mandatory folic acid fortification of certain foods; and lifestyle changes, such as smoking cessation during pregnancy and increased use of prenatal vitamins.^{Note 1, Note 2}

The greatest declines in the infant death rate were seen for circulatory system anomalies and spina bifida. For instance, infant deaths caused by circulatory system anomalies declined from a rate of 1.3 deaths per 1,000 births in 1974 to 0.3 deaths per 1,000 births in 2012. This decline was likely the result of increased early surgical repair.^{Note 2} For spina bifida, surgical intervention as well as the use of prenatal vitamins containing folic acid and the mandatory folic acid fortification in food products has resulted in fewer cases and, therefore, reduced the number of infant deaths from this congenital anomaly.^{Note 5, Note 9}

Infant deaths caused by chromosomal anomalies such as Down syndrome, and Edwards’ and Patau’s syndromes have remained relatively stable since 1974 (Chart 4). Chromosomal anomalies are less responsive to surgical treatment.^{Note 1}

Conclusion

Deaths caused by all congenital anomalies have decreased in Canada since 1974. Deaths from circulatory system anomalies and spina bifida have decreased the most during this time period. Prenatal screening, surgical intervention, as well as changes to prenatal care (such as folic acid supplementation) and folic acid fortification of certain foods have contributed to this decline. Deaths from chromosomal anomalies, which represent a small percentage of all infant deaths, have not changed over the studied time period probably because prevention efforts have had less of an impact on these anomalies. With the exception of Edwards’ and Patau’s syndromes, the average age at death from congenital anomaly is higher than it was in 1974.

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Tanya Navaneelan is an epidemiologist with Cancer Care Ontario, Caryn Pearson is an analyst with the Public Health Agency of Canada and Teresa Janz is an analyst with the Health Statistics Division at Statistics Canada.

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