Teratogens and Developmental Influences

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Teratogens and Other

Influences on Development

Scenario

You return after class one day to find a message in your voice mail from your cousin’s husband, who is obviously upset. He has called to tell you that your cousin, Karen has just given birth more than 2 months early to a little boy who weighs slightly less than 4 pounds.

Karen’s pregnancy had been planned and completely normal and she had followed her doctor’s advice to the letter, so this outcome comes as a complete shock. The baby has been moved to the neonatal intensive care unit.

You’re very close to Karen and know that she will want to see you as soon as possible.

When you visit her in the hospital, Karen tells you that the baby is in stable condition but that she’s deeply worried about what the future holds for him and for the family. She shares her fear that he will never have a normal life.

From what you’ve learned about pre-natal development in your child development class, what can you tell Karen about her new son’s chances for normal development? If she asks for your advice, what would you tell her?

Teratogens and Other

Influences on Development

Pregnancy and Alcohol

Terminology

Teratogen: any environmental agent that causes damage to the fetus during prenatal period.

viruses, drugs, chemicals, and radiation

others categories?

Terminology

95% of all newborns are born without problematic developments.

Of the remaining 5%,

3% have mild, temporary or reversible defects. only 2% having continuing effects.

Effect- What happens- the developmental outcome or

consequence of exposure to a teratogen

variation in the development of the embryo, fetus, or child.

Mechanism- How it happens- the physiological or

biological processes that explains the cause or how specific events occur

Terminology

Sensitive Period- That broad period of time

when, if an insult occurs, there are likely to be consequences.

– insults may occur over a broad period of time or in a number of ways e.g., the neurobehavioral effects due to exposure of alcohol during last trimester

Critical Period- A specific period of time during

which, if an insult occurs, a particular consequence will happen

– Malformation of ears due to thalidomide exposure on days 34-38 of PND.

Characteristics and Effects of Teratogens

Time of exposure

Worst effects= period when a body part or organ system is developing.

When is this?

Susceptibility to harm varies

Not all embryos or fetuses are affected in the same way by the same exposure.

Characteristics of the fetus influence the effects

Studies with identical twins frequently show that one twin has impairment from a teratogen while the other doesn’t.

Research on FAS shows that ½ ounce/day can cause neurobehavioral problems in some children, while some children born to alcoholic mothers don’t get FAS

Characteristics and Effects of Teratogens

Different teratogens can cause the same defect (equifinality)

– For example: ADHD may be caused by chronic stress experienced by the mother during pregnancy exposure to drugs during pregnancy exposure to alcohol during pregnancy

Characteristics and Effects of Teratogens

Single teratogen may cause more than 1 defect (multifinality)

– Rubella may cause blindness, deafness, and mental impairments

– Exposure to alcohol may cause physical malformations, growth retardation, and mental retardation.

Characteristics and Effects of Teratogens

Dose Response (more is worse than less)

FAS- Fetal Alcohol Syndrome

Associated with heavy drinking throughout pregnancy

Results- much more severe: physical malformations, major mental retardation

FAE- Fetal Alcohol Effects

Associated with binge drinking, or occasional drinking- Not as heavy, not as often

Results: Behavioral/emotional effects

Characteristics and Effects of Teratogens

Father’s exposure to teratogens also increases risk

WHY??????

Because sperm take 72 hours to mature and during this period the sperm are susceptible to malformations due to environmental exposures

Tetracycline (discolors the enamel of the infant’s teeth).

Typically associated with mom, but it is also true if dad takes it.

Characteristics and Effects of Teratogens

Long-term outcomes can be mediated by postnatal experience

– “Effect” may be a susceptibility

– Long term high quality care and enriched environment helps OVERCOME or minimize bad start

– HIV Babies with parents who were drug and alcohol users did better than non. WHY??

The Specifics

Diseases

Rubella-German Measles-

“Timing” is key

1st Trimester is likely to cause more serious impairments

Heart defects-

Cataracts-

1st 8 weeks (germinal/embryonic)

“ “

Deafness- last half of 1st trimester

Risk of having impairments (as well as the severity of them) decreases with time-

60-85% have impairments if exposed in the first 8 weeks

50% if exposed in the 3rd month

16% if exposed in the 2nd trimester

2nd Trimester

Minor mental deficiencies

Motor impairments hearing impairment

Diseases

Toxoplasmosis

–Beware of the household pet!!!

– 1st trimester

Severe CNS damage

Damage to the eyes and visual system

– Later trimesters increased miscarriage jaundice- problem with liver functioning- used to be major cause of MR pneumonia- inflammation of the lungs myocarditis

STDs

Syphilis (treatment matters!!!)

1st and 2nd trimester (<18 weeks) No effect if treatment clears infection.

Why?

The organism cannot cross the placenta < 18 weeks

2nd and 3rd trimester (>18 weeks)- impairs organs after they develop

Lesions of the eyes, optic nerve atrophy

Problems with the liver functioning

Bone malformations

Heart malformations

If present at birth, CNS impairment and gastrointestinal tract problems

STDs (read on own)

Chlamydia (timing doesn’t seem to matter)

– Infected mothers are more likely to miscarry or have stillborn infants

– If the disease is transmitted to the infant at birth, results in pneumonia and/or conjunctivitis-

Both “easily” treated

STDs(read on own)

Genital Herpes (23% of all adults have HSV 2, only

1/10 know they have it)

700,000 new cases each year

>350,000 new cases are women each year

80,500 women who are pregnant each year have new cases of HSV

1/15,000 births- neonatal HSV infection infected infants (EFFECTS):

1/3 of infants die

1/3 have permanent & moderate to severe brain damage

1/3 have mild impairments including liver probs, cns impairment, respiratory function

C-Section is recommended if infection is known pre-birth

HIV (read in your text, p. 99)

HIV

Can be latent for years (10-15 if you are in otherwise good shape)

Transmitted from mother to fetus either prenatally, at birth, or through the mothers milk (postnatally)

30% of pregnant women with HIV have babies who become infected.

8% transmission when mother uses AZT treatment during pregnancy and for the infant after birth

In twin studies where a vaginal delivery occurs, the first infant is 5X more likely to become infected-

Why?

Cesarean section is recommended

Hormones

Oral Contraceptives

– Cardiovascular problems

– 3-6 months off BEFORE pregnancy- Longer if you’ve been on the pill for a long time

Depo Provera

– 6-18mo

– Bone loss

Medications

DES (dielthystilbestrol)- Used to prevent miscarriages and premature deliveries

If prenatal exposure:

– Increased risk of cervical cancer in daughters- can be born with no uterus or fallopian tubes

– Increased risk of fetal feminization (one testicle, recessed testes) or hypospadias

– Higher rate of reproductive problems for both sons and daughters

Medications

– Thalidomide- drug used to stop morning sickness

Not pre-tested on pregnant humans

34-38 days malformations of the ears

38-46 days- malformations of the arms

40-46 days- malformations of the legs

Direction of development?

/

\

Good ex of cephal

Environmental Teratogens

What are they?

Methyl mercury- Pollutant found in fish

(very high quantities in some areas of

Japan, Puget Sound???)

– Increased birth weight

C-Sections

– Neurobehavioral effects (ADD, ADHD,

Learning disorder)

Environmental Teratogens

Lead Poisoning- found in old paint and water pipes

– Anemia- treatable

– Encephalopathy- abnormal development of the brain & MR

– Young children and infants who are lead poisoned can get MR-Method of ingestion?

Social Drugs

Alcohol- 43% of alcoholic mothers have FAS kids

(other 57% have FAE)

Full blown FAS:

– early exposure (specifically days 19-23)- results in facial dysmorphology- Diagnostic criteria wide set eyes (small eyes) thin upper lip flat filtrum

– repeated exposure, throughout pregnancy (early/late) microencephaly mental retardation (mild to severe) growth retardation (<10% on growth charts)

Late exposure (last trimester)

Decreased birth weight

Hyperactivity

Emotional lability (inability to control emotions/lots of emotional outbursts)

FAS

Social Drugs- Alcohol

MECHANISM- How does it work?

Mom’s ability to metabolize alcohol is reduced during pregnancy- decreases as pregnancy advances

– breakdown of alcohol uses extra oxygen- reduces the amount that is available to the developing organism

Alcohol can cross the placenta which impairs embryonic and fetal development

Fetus’s ability to metabolize alcohol is 50% of mom’s (so alcohol remains longer at the end of pregnancy)

Video- FAE

Social Drugs

Smoking (nicotine)

Effects

Decreased birthweight

Decreased heart rate increased spontaneous abortions increased perinatal mortality increased hyperactivity, ADHD, ADD

Patch??

Mechanism reduced oxygen available to the developing fetus-different ways

Increased heart rate and blood pressure

Social Drugs

Caffeine-

– Not as much known. Studies have conflicting results.

– Increases heart rate

– Increases blood pressure

– Constricts blood vessels

– Dehydrates, so probably reduces the oxygen supply

Illegal Drugs

Marijuana- small numbers of studies-

WHY?????

Moms who smoke during pregnancy

Attention may be impaired babies are smaller

Moms who smoke during pregnancy: have better parent-infant relationship at 1 month of age have calmer babies

Have better social interactions with the infant

Problem with the internal validity. Why??

Self-selected group

 may have more “relaxed” view of the world, so therefore have more “lax” relationship with the child

Illegal Drugs

Cocaine

Effects:

Decreased gestational age

Increased low birth weight

Placental abruption

Increased rates of birth defects- Malformations of the heart, CNS, gastrointestinal tract

Increased hyperactivity, ADD at school age.

Mechanism?

reduced oxygen supply

Study with 300 exposed & 300 non-exposed, controlling for SES found that Low SES had a greater effect on the infant development than cocaine.

Low B-W and Pre-term- Premature

Low birth weight and pre-term birth

Low birth weight= < 2500g or 5.5 lbs

Pre-term birth = < 35 weeks (post conception)- Not necessarily bad

Small for date

Influences on the size of the infant

Mother’s ht, wt

Mother’s age

Mother’s weight at birth

Environmental variables (teratogens?)

Nutrition

Birth order

Gestational weight, Birth weight, and Survival

Low Birth weight & survival

Weight at birth

1

– 1 ½ lbs

1 ¾ - 2 lbs

2 ¼ - 3 lbs

3

– 3 ½ lbs

>5 ½ lbs

% survival

33%

67%

84%

91%

98%

Pre-term birth & survival to 1 year

Gestational age @ birth

<24 weeks

24-25 weeks

26-29 weeks

30-32 weeks

33-36 weeks

37-40 weeks

41+ weeks

35%

63%

86%

93%

98%

99.3%

99.4 %

Birth weight

Babies BW

14 40

Maternal Age (in years)

<14 or >40, increased risk

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