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Teratogens

25 important questions on Teratogens

What is important about drawing conclusions from data about teratogens?

That it is always a population effect, you cannot really say anything about a single individual (for example, that someone has a learning disability because of alcohol).

What is the critical period for an organ?

The time in the development when that organ is developing (so that teratogen exposure in that period of time may cause defects in that organ).

When is the critical period for an embryo or fetus in the development of the central nervous system (CNS)?

From the 3rd week until the 38th week, with the period of the highest sensitivity between the 3rd and 8th week.

When is the critical period for an embryo or fetus in the development of the external genitalia?

From the 7th until the 38th week, with the most critical period between the 7th and 12th week.

What kind of effects do teratogens most likely have when the embryo is exposed to it (so between the 3rd and 8th week)?

Major structural abnormalities (because this is the moment where organs start to develop).

What kind of effects do teratogens most likely have when the fetus is exposed to it (so between the 12th and 38th week)?

Physiological defects and minor structural abnormalities.

What is thalidomide (1957-1961)?

A drug given to mothers to prevent morning sickness during the first trimester of pregnancy.

What happened when thalidomide was widely used?

An epidemic of phocomelia occured, babies were born without long bones of their arms and legs.

Why were arms and legs affected by thalidomide?

In the period that thalidomide was used (first trimester of pregnancy), arms and legs start to develop.

What are two other types of pharmacological teratogens?

Aspirin
Certain antibiotics

What type of antibiotics cause problems, and what kind of problems?

- Streptomycin and tetracycline
- can lead to hearing loss.

What can happen when a woman gets rubella in her first trimester of pregnancy?

20% of the embryos will get the infection too, which leads to congenital rubella syndrome.

What are some things children can get after getting a congenital rubella syndrome?

Cardiac defects, deafness,
eye anomalies,
(and when in very early pregnancy) spontaneous abortion, stillbirth

What gives a higher risk for greater malformations?

When the woman gets a rubella infection very early in pregnancy.

What is another infectious agent that can give problems to the embryo/fetus, and what does it cause?

- Zika virus,
- can cause severe microcephaly, and other major problems.

What were the findings of Ness, et al. (1999) about tobacco and cocaine as teratogens?

There was looked at 1000 pregnancies, of which 400 were a miscarriage. The findings were:

The self-reported cocaine use was not significantly related to miscarriage
Cocaine use determined by analysis of urine and hair samples showed that:

Cocaine use increased the probability of a miscarriage 1.4 times
Smoking increased probability of a miscarriage 1.8 times

What can alcohol consumption during pregnancy lead to?

The unborn child is also exposed to alcohol, because alcohol penetrates the placenta-fetus/embryo barrier.

What kind of animals with FAS show the same facial characteristics?

Mice.

What are two areas in the brain that are effected in children with FAS?

The Cerebellum and the Corpus Calosum (for example, permanent loss of tissue)

What are the type of structures in the brain that are typically deficient in children with FAS?

Midline structures (both shown in mice and humans)

What is an example of a midline structure that can also be effected in children with FAS?

The upper lip (cleft lip)

What does increase the risk of holoprosencephaly in certain species (humans?)?

Alcohol abuse during pregnancy.

What were three outcomes of studies in the 1990s on effects of alcohol drinking on embryological/fetal development?

Consumption of 2 or more alcohol drinks a day resulted in a, on average, 7-points decrement in IQ in 7-year-olds
Binge-drinking (once) leads to learning disabilities in 7-year-olds
Binge-drinking & exposure early in pregnancy is associated with adolescent antisocial behaviour, school problems, and self-perceived learning difficulties

What kind of studies are necessary for studying teratogens?

Large cohort studies

What kind of factors does research on teratogens in humans not exclude?

Multi-compound users, genetics, etc

The question on the page originate from the summary of the following study material:

Lectures Human Development

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