HUMAN REPRODUCTION BIOLOGY 269

1. HUMAN REPRODUCTIONBIOLOGY 269

2. Previous sessions: discussed normal embryonic and fetal development. Unfortunately, things don't always go right. More than 150,000 children born each year with birth defects, or congenital malformations. They are present in , and later become apparent in . Thus, they affect approximately

3. More than 4,000 different forms of birth defects known Can affect any organ and Often affect multiple organs They can be mild severe

5. Many possible causes: However, cause is unknown ~ half the time

6. Chromosomal abnormalities: Either: Since all cells of all organs have same chromosomes, chromosomal abnormalities often affect many different organs

7. Incidences of chromosomal abnormalities in spontaneously aborted fetuses and live births No. per 100 % surviving aborted to birth.... 3-4 sets of chromosomes 10 - 17 <0.01 Extra sex chromosome <1 >99 Missing sex chromosome 10 < 1 Extra autosome 20 - 40 3 Missing autosome 1 0 Damaged chromosome 2 - 3 35

8. Chromosomal abnormalities: Already talked about Can involve sex (X or Y) chromosomes or autosomal (other 44) chromosomes

9. Chromosomal abnormalities: Trisomy 21, or Down's Syndrome ~ 1 out of 660 live births Abnormal face, Abnormal hands, feet Heart defects Deafness Marked mental retardation

10. Chromosomal abnormalities: Turner's syndrome: X- ~ 1 out of 500 live births Short female; Poorly developed sexual characteristics Never enters puberty therefore sterile. Defects in heart, lungs, vessels, bones Occasionally mentally retarded

11. Chromosomal abnormalities: Abnormality (missing piece) of chromosome #5 Cri du chat syndrome Abnormal cry Small head & face Eye abnormalities Damage to brain Marked mental retardation

12. Drugs taken by mother; Cross placenta to embryo Hundreds of drugs known to cause birth defects. Potential for birth defects = most common reason drugs restricted

13. Best known = (sedative): Limb abnormalities Absent (whole or part), Short, Malformed Defects in heart, lungs, digestive system

14. Thalidomide

15. Examples of other drugs linked to birth defects: Aminopterin Defects of brain, nerves, or skeleton (often limbs) Methotrexate eyes, heart (antitumor agents) Diethylstilbesterol Defects of uterus, vagina ( ↓ miscarriage) Vitamin A Defects of brain, spinal cord, face (cleft palate/lip), heart Streptomycin Deafness from damage to (antibiotic) inner ear

16. Defects of

18. Diseases and infections of mother may cause birth defects, including many diseases which are relatively mild to her Bacteria, viruses, etc. may cross placenta to embryo or Antibodies produced by mother's immune system may cross placenta and damage embryo

19. Some common diseases linked to birth defects Defects of head & face, brain, eyes, other organs Defects of eyes, brain, heart Deafness Defects of eyes, head, brain

20. Examples of chemicals in food, air, water linked to birth defects Cross placenta to embryo Defects of brain, nerves, heart Defects of skeleton (often limbs) Blindness, deafness Spasticity Mental retardation Defects of heart, brain Blindness, deafness Decreased fetal growth Defects of face (cleft palate/lip) Emotional & learning problems

21. Methylmercury poisoning Minamata Japan, 1930s-1950s

22. Physical trauma to fetus can cause defects: Dislocated hip, shoulder Deformed limbs Deformed skull Amputation of limbs

23. Leg and foot deformities Inadequate amniotic fluid and uterine pressure

24. Cord around neck

25. Again: Cause