Teratogens

1. Teratogens

2. Terminology • Defn: any environmental agent that causes damage to the fetus during prenatal period. • viruses, drugs, chemicals, and radiation • others categories?

3. Terminology • 95% of all newborns are normal. 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 explain the cause or how specific events occur

4. 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.

5. 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

6. 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

7. 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.

8. Characteristics and Effects of Teratogens • Dose Response (more is worse than less) • FAS- Fetal Alcohol Syndrome • Associated with heavy drinking throughout pregnancy • physical malformations • may have major mental retardation • FAE- Fetal Alcohol Effects • Associated with binge drinking, or occasional drinking- Not as heavy, not as often • Behavioral effects- ADHD, less ability to control emotions

9. 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.

10. Characteristics and Effects of Teratogens • Long-term outcomes can be mediated by postnatal experience • Initial effects seem to be more severe • “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??

11. Environmental Teratogens • What are they? • Methyl mercury- Pollutant found in fish (very high quantities in some areas of Japan) • Increased birth weight  C-Sections • Neurobehavioral effects (ADD, ADHD, Learning disorder)

12. 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- Eating the paint off the walls

13. 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)

14. 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- Occurs by collapsing the umbilical cord • 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)

15. Video- FAE

16. Social Drugs • Smoking (nicotine) • Effects • Decreased birthweight • Decreased heart rate • Increased carbon monoxide in mom’s system, impairs oxygen exchange and crosses the placenta- Book study • increased spontaneous abortions • increased perinatal mortality • increased hyperactivity, ADHD, ADD • Mechanism • reduced oxygen available to the developing fetus • Decreased heart rate and blood pressure

17. 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

18. 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

19. Illegal Drugs • Cocaine • Effects: • Decreased gestational age • Pre-term, 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 • Recent study with 300 exposed & 300 non-exposed, controlling for SES found that Low SES had a greater effect on the infant development than cocaine.

20. Low B-W and Gest Age • Low birth weight and pre-term birth • Low birth weight= < 2500g or 5.5 lbs • Pre-term birth = < 35 weeks- Not necessarily bad • Influences on the size of the infant • Mother’s ht, wt • Mother’s age • Mother’s weight at birth • Environmental variables • Nutrition • Birth order

21. Babies BW 14 40 Maternal Age (in years) Birth weight • <14 or >40, increased risk

22. Gestational weight, Birth weight, and Survival Low Birth weight & survival Weight at birth % survival 1 – 1 ½ lbs 33% 1 ¾ - 2 lbs 67% 2 ¼ - 3 lbs 84% 3 – 3 ½ lbs 91% >5 ½ lbs 98% Pre-term birth & survival to 1 year Gestational age @ birth <24 weeks 35% 24-25 weeks 63% 26-29 weeks 86% 30-32 weeks 93% 33-36 weeks 98% 37-40 weeks 99.3% 41+ weeks 99.4 %