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 Pregnancy and Alcohol 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 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- 1st 8 weeks (germinal/embryonic) Cataracts-“ “ Deafness- last half of 1st trimester –Risk of having impairments (as well as the severity of them) decreases with time % 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 days malformations of the ears\ days- malformations of the arms 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)

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? Environmental Teratogens

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% survival 1 – 1 ½ lbs33% 1 ¾ - 2 lbs67% 2 ¼ - 3 lbs84% 3 – 3 ½ lbs91% >5 ½ lbs98% Pre-term birth & survival to 1 year Gestational birth <24 weeks35% weeks63% weeks86% weeks93% weeks98% weeks99.3% 41+ weeks99.4 %

Birth weight 40, increased risk 40, increased risk Babies BW Maternal Age (in years)