Epidemiology and etiology of birth defects

Question 1

Define epidemiology

Answer 1

The study of the distribution of determinants of health(physical , biological ,social ,cultural ect) in a specific population

Question 2

What is the scope of epidemiology ?

Answer 2

• definition
• occurrence
• cause
• outcome
• management
• prevention

Question 3

Explain the concept of health transition ?

Answer 3

A congenital abnormality or a birth defect is a structural / functional abnormality that is present at birth but which may manifest at any point during an individual s lifetime

There are major and minor congenital abnormalities .

A major / serious congenital abnormality is the one which may lead to disability or death

Question 4

What is the difference between incidence / birth prevalence and population prevalence ?

Answer 4

Incidence : Number of new cases of disease over a period of time

Population prevalence : Number of existing cases of a disease at a give point

Question 5

State the occurrence of the heath state

Answer 5

*WHO estimates that 3-6 % of babies are born with congenital abnormalities (7.9 millions )

Mortality : 30 -50 % with serious birth defects will die

Question 6

Briefly discuss the burden of congenital disorders in SA ?

Answer 6

• In Sa few registrations for birth defects surveillance
• poor data collection
• Modelled data indicates 6,8% birth prevalence of congenital disorders
• Equates to 1 to 15 live births
• Birth defects are the 3rd leading cause on neonatal mortality

Question 7

What are the causes of the health state

Answer 7

1. Pre-conception (90% genetics/ partly genetics)
   >Chromosomal abnormalities
   >Single gene defects
   >Multifactorial abnormalities

2.Post-conception (5-10% non-genetics)
>Teratogenic exposures (physical agents ,chemical agents ,maternal medical conditions and infectious diseases )

> Uterine constraints / environment

Question 8

What are the factors influencing the prevalence of birth defects

Answer 8

1.Consanguineous marriages : 20% of the world population practice consanguinity and thus 8,4 % of the world’s children have related parents
Eastern Mediterranean ,North Africa and India sub-continent

Parental consanguinity increases birth prevalence of autosomal recessive defects( neonatal birth and death defects ,intellectual disability and serious birth defects is almost doubled in first cousins )

2. Parental Age ( maternal age): As a women age the chances of non-disjunction in her oocyte increase, as a result those oocytes are polyploid= increase chances of polyploid defects eg Down Syndrome (>40 ages )
3. Migrations : The displacement of a proportion of a population to a new geographical area, if there is a prevalent genetic condition in the displaced population , more prevalent in the new generation due to loss of genetic variation
4. Urbanization : Affects the lifestyle of people who move to urban areas causing them to adapt unhealthy habits such as lack of exercise resulting in life style associated diseases which might cause birth defects

5.Malaria : Prevalence of malaria in the certain areas of the world influences the prevalence of certain birth defects in these carriers. Compared to non-carriers ,healthy carriers of the recessive genes for sickle cell anemia ,thalassemia and G6PD deficiency have a well documented survival advantages against effects of malaria, as a result carriers reach a reproductive age
the birth prevalence of thalassemia, sickle cell disease and G6PD deficiency is high in malaria endemic regions of the world like sub-Saharan Africa, the Eastern Mediterranean and North Africa, Southeast Asia and Western Pacific regions.

6. Poverty and National level of healthcare
   * Micro and macro nutrients deficiencies
   * Increased burden of infectious disease
   * reduced access to vaccination
   * increased burden of alcoholism
   * Less screening / preventative care

Question 9

Effects of advanced maternal age

Answer 9

Birth prevalence of down syndrome in low - middle income countries is 2-3/ 1000 live births

Advanced maternal age pregnancies accounts for 11-18% of pregnancies in low and middle income countries

Question 10

Management of the health state

Answer 10

1.Make an early diagnosis
>Early recognition of abnormality
>Appropriate investigation
>Appropriate referral

2.Offer the best possible treatment available
>Surgery
>Palliative therapy
>Remedial therapy (Should take place as close close to patient home )
>Access to social services

3.Provide genetic counselling
>provide information and psychological support

Question 11

Prevention of health state

Answer 11

1. Primary prevention :
   * Health education
   * Optimize maternal diet for necessary micro and macro nutrients
   * Family planning
   * Detection and treatment of maternal infections and vaccination
2. Secondary prevention ( to reduce number of children born with birth defects ) : Medical genetic screening and prenatal diagnosis and screening
3. Tertiary prevention ( treatment of children with birth defects ): Surgery ,remedial therapy ,palliative care and new borne screening