Outline the stages of prenatal development and discuss the environmental risks that may impact upon the developing fetus

Question 1

How would you structure an essay outlining the stages of prenatal development and discussing the environmental risks that may impact on the developing fetus?

Answer 1

1. Introduce structure
2. Stages of prenatal developments (introduce, zygote, embryo, fetus)
3. Teratogens (introduce, diseases, drugs, environmental hazards)
4. conclusion

Question 2

How many stages is prenatal development divided into?

Answer 2

3

Question 3

What is the first stage of prenatal development called? How long does it last?

Answer 3

The period of the zygote

Lasts from conception through implantation - 10 - 14 days

Question 4

What is the second stage of prenatal development called? how long does it last? what mainly happens during this phase?

Answer 4

1. Period of the embryo
2. beginning of 3rd week - end of 8th week
3. Virtually all major organs formed and heart begins to beat

Question 5

What is the 3rd stage of prenatal development called? how long does it last? what mainly happens during this phase?

Answer 5

1. the period of the fetus
2. lasts from the 9th week of pregnancy until the baby is born.
3. During this phase all the major organ systems begin to function, and the developing organism grows rapidly.

Question 6

What happens in the first week? (period of zygote - 3 points)

Answer 6

1. In the first week, as the fertilized ovum, or zygote, moves down the fallopian tube toward the uterus, it divides by mitosis into two cells
2. These two cells and all the resulting cells continue to divide, forming a ball-like structure, or blastocyst, that will contain 60 to 80 cells within 4 days of conception.
3. Cell differentiation has already begun, the inner layer of the blastocyst will become the embryo, and the outer layer of cells will develop into tissues that protect and nourish the embryo.

Question 7

What happens in the second week?

Answer 7

In the second week the blastocyst implans into the uterine wall; and structures that nourish and protect the organism, such as: amnion, chorion, yolk sac, placenta, and umbilical cord, begin to form.

Question 8

What structures that nourish the organism begin to form in the second week? (p of zygote)

Answer 8

Amnion
chorion
yolk sac
placenta
umbilical cord

Question 9

How long does period of embryo last?

Answer 9

The period of the embryo lasts from implantation (roughly the third week) through the 8th week of pregnancy.

Question 10

What is happening in the third week? (period of the embryo)

Answer 10

By the 3rd week the embryonic disk is rapidly differentiating into three cell layers: ectoderm, mesoderm, and endoderm

Question 11

What is the outer layer of the embryonic disk called? What does it become?

Answer 11

Ectoderm

It will becomes the nervous system, skin and hair

Question 12

What is the middle layer of the embryonic disk called? What does it become?

Answer 12

Mesoderm

It will become the muscles, bones, and circulatory system

Question 13

What is the inner layer of the embryonic disk called? What does it become?

Answer 13

Endoderm

It will become the digestive system, lungs, urinary tract, and other vital organs such as the pancreas and liver

Question 14

What happens in weeks 3-4 (period of embryo - 3 points)

Answer 14

1. Embryo grows to .25 inches
2. Brain, spinal cord and heart form

3. as do the rudimentary structures that will becomes the:
eyes
ears
nose
mouth
limbs

Question 15

What happens in weeks 5-8? (period of embryo - 5 points)

Answer 15

1. Grows to 1 inch
2. External body structures form
3. Internal organs form
4. Embryo now produces its own blood
5. Embryo can now move

Question 16

How long does the period of the fetus last?

Answer 16

The last 7 months of pregnancy

Question 17

The last X months of pregnancy, or the period of the fetus, is a period of rapid [blank] and [blank] of all organ systems

Answer 17

7

growth

refinement

Question 18

Broadly what happens during the period of the fetus? (2 sentences)

Answer 18

1. all major organ systems begin to function and the fetus begins to move, sense, and behave (although not intentionally).
2. individuality emerges as different fetuses develop unique characteristics, such as different patterns of movement and different facial expressions

Question 19

What happens in weeks 9-12 of the period of the fetus? (3 points)

Answer 19

1. The fetus grows to 3 inches
2. Rapid growth and interconnections of all organ systems permits new competencies:
   - body and limb movement
   - swallowing
   - digestion of nutrients
   - urination
3. External genitalia form now too

Question 20

What happens in weeks 13-24 of the period of the fetus? (5 points)

Answer 20

1. Grows to 14-15 inches
2. Fetal movements felt by mother
3. Fetal heartbeat can be heard
4. Fetus is covered by vernix to prevent chapping
5. Reacts to bright lights and sounds

Question 21

What happens in weeks 25-38 of the period of the fetus? (6 points)

Answer 21

1. Grows to between 19-21 inches
2. Weighs 7-8lbs as organs mature in preparation for birth
3. Reaches age of viability
4. Becomes predictable in its sleep cycles and motor activity
5. Layer of fat develops under the skin
6. Activity becomes less frequent as the baby sleeps more in the last 2 weeks before birth

Question 22

How many sub-sections can you divide the period of the fetus into? (weeks)

Answer 22

3

9-12
13-24
25-38

Question 23

What % of newborn infants follow the ‘normal’ pattern of prenatal development?

Answer 23

95%

Question 24

What does the term teratogen refer to?

Answer 24

The term teratogen refers to any disease, drug, or other environmental agent that can harm a developing embryo or fetus by causing physical deformities, severely retarded growth, blindness, brain damage, or even death (Fifer, 2005).

Question 25

The list of known and suspected teratogens has grown very long over the years; however…

Answer 25

it is important to emphasise that 95% of newborn babies are perfectly normal, and that many of those born with defects have mild, temporary, or reversible problems (Gosden, Nicolaides, & Whitting, 1994).

Question 26

each major organ system or body part has a sensitive period when it is most susceptible to teratogenic agents - when is this usually?

Answer 26

the time when that particular part of the body is forming (most organs and body parts are rapidly forming during the period of the embryo)

Question 27

Once an organ or body part is fully formed, it becomes less susceptible to damage. However…

Answer 27

some organ systems (particularly the eyes, genitals and nervous system) can be damaged throughout pregnancy.

Question 28

Further, in research looking at birth defects and drugs in pregnancy, Heinonen and colleagues (1977) concluded that …

Answer 28

that many of the birth defects found among the 50,282 children in their sample were ‘anytime malformations’ - problems that could have been caused by teratogens at any point during the 9 month prenatal period

Question 29

What are the three kinds of teratogens we are going to look at?

Answer 29

diseases
drugs,
environmental teratogens.

Question 30

Some disease agents are capable of crossing the X and doing much more damage to a developing embryo or fetus than to the pregnant woman herself

Answer 30

placental barrier

Question 31

Some disease agents are capable of crossing the placental barrier and doing much more damage to a developing embryo or fetus than to the pregnant woman herself. This makes sense when we consider that… (2 points)

Answer 31

an embryo or fetus has an immature immune system that cannot produce enough antibodies to combat infections effectively, and that the fetal environment may react differently to infections than the pregnant woman’s immune system does.

Question 32

No infections are more common, and few are more hazardous to the fetus than…

Answer 32

sexually transmitted infections.

Question 33

According to one estimate, as many as X million adolescents and adults in the United States either have or have had a sexually transmitted disease (STD) that is capable of producing serious birth defects. Who estimated this?

Answer 33

32

Cates, 1995

Question 34

Three of these diseases: X, Y, and Z - are particularly hazardous.

Answer 34

1. Syphilis
2. Genital Herpes
3. Acquired Immunodeficiency Syndrom

Question 35

If untreated, what can syphilis cause?

Answer 35

1. miscarriage

2. Serious defects including eye, ear, bone, heart, or brain damage

Question 36

What did Artistotle note in relation to drunken mothers? Says who?

Answer 36

That they had ‘feeble-minded babies’ (Abel, 1981)

Question 37

now we know that alcohol affects the development of the fetus directly and indirectly by…

Answer 37

compromising the function of the placenta

Question 38

In 1973 X and colleagues described a Y that affects many children of alcoholic mothers.

Answer 38

Kenneth Jones

Fetal Alcohol Syndrome

Question 39

What are the most noticeable characteristics of fetal alcohol syndrome?

Answer 39

1. Microcephaly

2. Malformations of the heart, limbs, joints and face

Question 40

FAS babies are likely to display what 4 things?

Answer 40

1. excessive irritability
2. hyperactivity
3. seizures
4. tremors

Question 41

FAS babies are also X and Y than normal, and their physical growth lags behind that of normal age-mates.

Answer 41

smaller

lighter

Question 42

Finally, the majority of the X in Y babies born with FAS score well below average in intelligence throughout childhood and adolescence, and more than Z% of them display [blank]

Answer 42

3 in 1000

90%

major adjustment problems as adolescents and young adults

Question 43

It is not just recreational drugs that have teratogenic effects -

Answer 43

some of the most commonly used over-the-counter-drugs have suspected negative effects on the developing fetus.

Question 44

Heavy use of aspirin, for example, has been linked to …

Answer 44

fetal growth retardation, poor motor control and even infant death (Barr et al., 1990);

Question 45

the use of ibuprofren in the third trimester increases the risk of…

Answer 45

a prolonged delivery and pulmonary hypertension in newborns (Chomitz, Cheung and Lieberman, 2000).

Question 46

What do environmental hazards as teratogens include?

Answer 46

chemicals in the environment that the pregnant woman cannot control and may not even be aware of, as well as some that she can regulate.

Question 47

What is probably the most well known environmental hazard for the developing fetus?

Answer 47

Radiation

Question 48

How did the harmful effects of radiation to the developing fetus come to light?

Answer 48

following the atomic blasts of 1945 in Japan

Question 49

What happened to preganant women within half a mile of the 1945 atomic blast in Japan?

Answer 49

Not one gave birth to a live child

Question 50

What happened to preganant women within 1.25 miles of the 1945 atomic blast in Japan?

Answer 50

75% of the pregnant women who were within 1.25 miles of the blasts had seriously disabled children who soon died, and those who did survive were often mentally retarded (Apgar & Beck, 1974).

Question 51

Less understood environmental hazards that pregnant women come in contact with on a regular basis include what four things? Why are they thought to have teratogenic effects?

Answer 51

food additives, artificial sweetners, pesticides, and cosmetic products,

some of which are known to have teratogenic effects in animals.

Question 52

Unfortunately, the risks associated with a large number of these common chemical additives and treatments ….

Answer 52

remains to be determined.

Question 53

To conclude…. (2 sentences)

Answer 53

In answering this question we first introduced the three stages of prenatal development, before exploring environmental risks that may impact on fetal development. The environmental risks we explored were: diseases, drugs and environmental hazards.