1. Period of the Fetus Lasts from the ninth week post-conception until the end of pregnancy (approximately 38 weeks)

2. Between approximately 9-12 weeks: –Organs, muscles, and nervous system start to become organized and connected By about 12 weeks, fetus engages in most movements that are present at birth –Exs: kicking, thumb-sucking, grasping, swallowing –Expansion and contraction of lungs (“fetal breathing”) –Sexual differentiation has begun Sex of the fetus can be detected with ultrasound by approximately 12 weeks

3. Period of the Fetus (2 nd trimester): Between approximately 16-20 weeks, mother starts to feel movement of fetus

4. Period of the Fetus (3 rd trimester): Fetus triples its weight during the last trimester –Brain growth also continues Cerebral cortex enlarges Fetus reacts to a variety of sounds Age of viability: The point at which a fetus can first survive outside the womb –Approximately 22-26 weeks (with medical intervention)

5. Period of the Fetus (3rd trimester) con’t: Near the end of pregnancy, fetus is awake more often than earlier in pregnancy –But still spends most of its time sleeping (like newborns) REM sleep is present Fetal activity level is correlated with infant activity level

6. Teratogen: Any environmental agent that can cause damage during the prenatal period

7. General Principles of Teratogenic Effects: Dose: Larger doses over longer time periods usually have more negative effects Heredity: The genetic makeup of the mother and embryo/fetus influence the effect of a teratogen

8. Timing: Effects of a teratogen vary with the age of the organism at the time of exposure –Sensitive Period: Time during which basic structures are being formed Each major organ system has its own sensitive period –An organ system is most vulnerable to teratogens during its sensitive period

10. Cumulative Risk: Effect of a teratogen may be worse if there are other risk factors present (e.g., poor nutrition, lack of medical care, other teratogens)

11. Tobacco: Most consistently associated with low birth weight, which is a risk factor for other developmental problems

12. Tobacco: Mechanisms Nicotine constricts blood vessels –Reduces blood flow to the uterus and causes placenta to grow abnormally Reduces the transfer of nutrients to the fetus Nicotine raises the concentration of carbon monoxide (and decreases oxygen) in mother’s and fetus’ bloodstreams –Likely to slow fetal growth and may damage CNS

13. Fetus exposed to carcinogens contained in tobacco

14. Fetal Alcohol Syndrome: Facial abnormalities and small head Slow physical growth and small size Mental retardation and/or other cognitive impairments (in memory, attention, language) Hyperactivity Impaired motor coordination

15. Alcohol: Mechanisms Interferes with brain development A woman’s body requires a lot of oxygen to metabolize alcohol –Fetus gets less oxygen