T2 L24 Congenital Abnormalities and Teratology Flashcards
Define “congenital anomaly”
Abnormality of structure, function or disorder of metabolism that is present at birth and results in a physical or mental disability
List alternative names for “congenital anomaly”
- birth defects
- clinical dysmorphologies
- congenital anomaly
- congenital malformation
What is “teratology”?
Study of causes and biological processes leading to abnormal development at fundamental and clinical level, and appropriate measures for prevention
Define “incidence”
Number of new cases in a given population over a specific time period
NOTE: not able to identify ALL new cases (miscarriage etc) and unable to measure all pregnancies so prevalence is used instead
What is birth prevalence?
Birth prevalence means (fetal loss, stillbirth, TOPs (termination of pregnancies) and births) per 10,000 births
When can a congenital anomaly be identified?
May be identified prenatally, at birth, or sometimes may only be detected later in infancy, such as hearing defects
How many newborns die within 4 weeks of birth every year, worldwide, due to congenital anomalies?
303,000
What impact can congenital anomalies have?
Contributes to long-term disability
Causes significant impacts on individuals, families, health-care systems, and societies.
What are the most common, severe congenital anomalies?
Heart defects
Neural tube defects
Down syndrome
What % of congenital anomalies have no known causes?
50%
What are the risk factors for congenital anomalies?
Genetic – inherited vs sporadic mutation. NB consanguinuity
Infectious – Rubella, Syphilis, Zika
Teratogens
Socio-economic / demographics - nutritional (eg folatic acid) or environmental factors, age
What measures can be taken to protect against some congenital anomalies?
Vaccination (Rubella)
Adequate intake of folic acid or iodine through fortification of staple foods or supplementation
Appropriate Antenatal care
What does consanguinity increase the risk of?
Increases the prevalence of rare genetic congenital anomalies
Nearly doubles the risk for neonatal and childhood death, intellectual disability and other anomalies
What % of of severe congenital anomalies occur in low- and middle-income countries?
94%
Why does a large proportion of congenital anomalies occur in in low- and middle-income countries?
- lack of access to sufficient, nutritious foods by -pregnant women
- an increased exposure to agents or factors such as infection and alcohol
- poorer access to healthcare and screening
What affect does advanced maternal age have on the risk of chromosomal abnormalities, including Down syndrome?
It increases the risk
Which types of congenital abnormalities pose the greatest problems?
- Congenital heart defects
- Chromosomal abnormalities
How are structural abnormalities classified?
MALFORMATION: flawed development of a structure or organ (eg. transposition of the great arteries)
DISRUPTION: alteration of an already formed organ (due to a vascular event like poor blood supply e.g. bowel atresia)
DEFORMATION: alteration in structure caused by extrinsic pressures (mechanical eg talipes due to reduced liquor. Can also be caused by an amniotic band which constricts around the limb, preventing it from receiving enough blood supply)
DYSPLASIA: abnormal organisation of cells or tissues
What is a syndrome?
Multiple congenital abnormalities
Group of abnormalities due a single aetiology
e.g. single chromosomal/gene problem
What is a sequence?
Multiple congenital abnormalities but as a consequence of one abnormality
e. g. Potters sequence:
- renal agenesis leading to oligohydramnios
- leading to skeletal deformities
What facial features does a Down syndrome (T21) child have?
- small nose and flat nasal bridge/ flat face
- large tongue that may stick outof mouth
- eyes that slant upwards and outwards
- a flat back of the head / thickened skin on the back of the neck
What other external features does a Down syndrome child have?
- broad hands with short fingers
- single palmar crease
- below-average weight and length at birth
What other problems are associated with Down syndrome?
- Cardiac defects
- Duodenal atresia
- Mild to moderate learning disability
Why is the number of Down syndrome babies being born decreasing?
More people are choosing to abort their Down syndrome baby
What facial abnormalities do Edward’s syndrome (T18) children have?
- small
- abnormally shaped head
- small jaw and mouth
- low-set ears
- cleft lip/palate
What skeletal abnormalities do Edward’s syndrome children have?
- long fingers that overlap
- underdeveloped thumbs
- clenched fists
What gastrointestinal abnormalities do Edward’s syndrome children have?
- omphalocele
- oesophageal atresia ± tracheo-oesophageal fistula
- umbilical or inguinal hernia
- pyloric stenosis
NOTE: Omphalocele occurs when the abdominal content grows outside the abdominal cavity
What urogenital abnormalities do Edward’s syndrome children have?
- gonadal dysgenesis
- horseshoe kidney
- hydronephrosis
- cystic kidneys
- renal agenesis
What neurological problems do Edward’s syndrome children have?
- anencephaly
- hydrocephaly and other brain malformations
- severe learning disability
- seizures
What % of Edward’s syndrome children will have congenital heart defects?
> 90%
NOTE: Edward syndrome children typically die within their first year
What pulmonary abnormality do Edward’s syndrome children have?
Pulmonary hypoplasia
What % of Patau’s syndrome children will have congenital heart defects?
> 80%
What facial abnormalities do Patau’s syndrome (T13) children have?
cleft lip / palate
abnormally small eye or eyes (microphthalmia) or
absence of 1 or both eyes (anophthalmia)
reduced distance between the eyes (hypotelorism)
microcephaly
What gastrointestinal abnormalities do Patau’s syndrome children have?
omphalocele
exomphalos
NOTE: Exomphalos is a weakness of the baby’s abdominal wall where the umbilical cord joins it. This weakness allows the abdominal contents, mainly the bowel and the liver to protrude outside the abdominal cavity where they are contained in a loose sac that surrounds the umbilical cord
What CNS disorders do Patau’s syndrome children have?
holoprosencephaly (no septum between the brain) – single brain
What skeletal abnormalities do Patau’s syndrome children have?
extra fingers or toes (polydactyly)
a rounded bottom to the feet (known as ‘rocker-bottom’ feet)
When do babies with Patau’s syndrome typically die?
Within days of birth
What is teratogen?
an agent (such as a virus, a drug, or radiation) that causes malformation of an embryo or foetus
Which teratogen can cause microcephaly?
Zika virus
COMPLETE THE SENTENCE
Warfarin is a teratogenic _____ and it causes _________
Drug
Chondrodysplasia, microcephaly
COMPLETE THE SENTENCE
_________ is a teratogenic ________ and it causes limb defects/heart defects
THALIDOMIDE
Drug
What is rubella and what does it cause?
A virus
Causes rubella (deafness)
What type of teratogenic agents are pesticides? What is their effect?
Chemicals
Causes neural tube defects
What type of teratogenic agent is hyperthermia? What is its effect?
Physical agent
Causes fetal death, neural tube defects
COMPLETE THE SENTENCE
Radiation is a teratogenic ________ and it causes ___________
Chemical
Microcephaly, spina bifida
COMPLETE THE SENTENCE
_________ is a teratogenic ________ and it causes FAS (maxillary hypoplasia, mental retardation)
Alcohol
Chemical
What type of teratogenic agent are androgens? What is their effect?
Hormone
Causes masculinisation of external genitalia
What are the facial features of Foetal Alcohol Syndrome (FOS)?
- epicanthal folds
- flat nasal bridge
- small palpebral fissures
- “railroad track” ears
- upturned nose
- smooth philtrum
- thin upper lip
What % of congenital abnormalities are detected antenatally?
61%
What % of congenital abnormalities are detected at birth?
8%
What % of congenital abnormalities are detected at 2-4 weeks?
6%
What % of congenital abnormalities are detected after the first month?
18%
Why detect congenital abnormalities?
Termination
Treatment
Time Delivery: diabetes
Preparation for parents – eg. Downs group / support
What treatment is available if congenital abnormalities are detected?
In utero (correction of): cleft palate/ pulmonary shunts /tumours, transfusions, balloon occlusion of diaphragmatic hernia
Maternal: Antibiotics (eg for toxoplasmosis)
Post-delivery: CHD deliver in tertiary centre for immediate surgery
