Birth Defects Flashcards by Esme Cosham

How common are human birth defects?

1 in 44 births in UK

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When are women most vulnerable?

During embryonic period (E) - around weeks 3-8. Before this, foetus would die, after this most systems are developed.

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Which system is most vulnerable to birth defects and why?

CNS - develops over long period of time

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What causes congenital malformations and what %?

Unknown - 50%
Genetic - 18%
- Chromosomal 10%
- Monogenic 8%
Environmental 7%
Multifactorial (combination of genetic &amp; environment) 25%

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What happens during chromosomal problems?

Problems during chromosomal separation or misalignment. Can be numerical or structural.

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What happens during monogenic problems?

Defective gene on autosome that is inherited

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What happens during Trisomy 21 - Down’s syndrome?

Failure of 21st chromosome to separate, producing an extra copy of chromosome 21. The cell therefore has 24 chromosomes.

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What are the problems associated with Trisomy 21?

Growth retardation, intellectual retardation, craniofacial abnormalities, congenital heart defects.

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What are environmental causes called?

Teratogens

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What are the classifications of infectious causes?

Infections that can cross the placenta.

TORCH - Toxoplasmosis, Other (syphilis, Hep B), Rubella, Cytomegalovirus, Herpes.

Zika virus is considered newest addition.

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Toxoplasmosis. How? Where? Symptoms?

Mother contracts parasite during embryonic period. Found in cat faeces, undercooked/raw meat. Usually asymptomatic.

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What are congenital malformations in foetus as a result of T?

Inflammation of retina and eye
Hearing loss
Enlarged liver / spleen
Hydrocephaly
Microcephaly

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What is hydrocephaly?

Fluid on brain pushes skull bones apart.

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What is microcephaly?

Head and brain don’t form correctly (smaller than usual)

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Rubella. How? When?

Infection passes over placenta in first 3 months of pregnancy. Rates have fallen since MMR vaccine.

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Congenital malformations as a result of R?

Cloudy cornea
Intellectual disability
Microcephaly
. Heart defects

Cytomegalovirus. How? Symptoms?

Virus crosses placenta. Infection via bodily fluids: semen, blood, sweat. Usually asymptomatic.

Congenital malformations as a result of C?

Inflammation of retina/microphthalmia
Enlarged spleen/liver
Mineral deposits on brain (e.g. calcium)

Herpes. How? When?

Herpes Simplex - Usually doesn’t travel up reproductive system of female, instead transferred to baby at birth.

Varicella Zoster Virus - Causes chickenpox. Most dangerous between 13-20 weeks of pregnancy, just before birth and up to 2 days postpartum.

Congenital malformations as a result of H?

Segmental skin loss / scarring
Limb hypoplasia / paresis
Microcephaly
Visual defects

Zika virus. How? Symptoms?

Mosquito bite, transmits through bodily fluids. Fever, rash, joint pain, red eyes but can also be asymptomatic.

Congenital malformations as a result of zika?

Microcephaly

- Severe cognitive disabilities

What are the chemical causes of birth defects?

Thalidomide and alcohol

What was thalidomide used to treat and what were the results? Where is it still used?

Prescribed for morning sickness. Lead to shortened or absent limbs in children. Now used to treat leprosy and HIV (e.g. in Brazil)

What can consumption of alcohol during pregnancy lead to?

Can cause foetal alcohol syndrome. - Prenatal and postnatal growth retardation - Intellectual disability - Impaired motor ability and coordination

What are dangers of radiation exposure during pregnancy? Which system is most vulnerable?

Causes premature cell death or chromosomal changes. CNS is most sensitive.

What are the congenital malformations as a result of radiation?

- Microcephaly - Mental and cognitive disabilities - Haemopoietic malignancies and leukaemia

What happens during diabetes mellitus? What effects can it have?

There is a problem with glucose crossing over the placenta and controlling the amount of glucose. Can cause cellular structural defects and changes in cellular physiology

Congenital malformations as a result of diabetes?

- Macrosomia (enlarged baby) - Ventricular septal defects (within heart) - Spina bifida (neural tube defect) - Renal agenesis (failure of mature kidney formation)

What can a deficiency in folic acid in women lead to? What are the congenital malformations?

Can cause problems with the development of the CNS. - Spina bifida - Anencephaly

What is spina bifida?

Poor development of spine and spinal cord, causing a gap in the spine

What is anencephaly?

Large past of skull and cerebral hemisphere of brain are absent.

How is folic acid deficiency combatted?

OTC supplements reduce risk of malformation by 60%. Many countries impregnate food with folic acid.

What are teratogens?

Teratogen: Any agent that can disturb the development of an embryo or fetus. Teratogens may cause a birth defect in the child. Or a teratogen may halt the pregnancy outright. The classes of teratogens include radiation, maternal infections, chemicals, and drugs.

Which infection is usually transferred to the baby at birth instead of travelling up the reproductive tract?

Herpes Simplex

What is the Varicella Zoster virus?

It causes chickenpox, also called varicella and shingles,