1. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Children Prenatal Development 3

2. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. The Germinal Period First two weeks after conception –Creation of zygote –Blastocyst inner layer of cells develops into embryo –Trophoblast outer layer of cells that develops during germinal period, nourishes embryo The Course of Prenatal Development

3. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. The Embryonic Period Two to eight weeks after conception Cell differentiation occurs, embryo has three layers of cells –Endoderm: inner layer of cells form digestive and respiratory –Ectoderm: outermost layer forms skin parts, nervous system, and sensory receptors –Mesoderm: middle layer forms circulatory, bones, muscles, reproductive systems, etc. The Course of Prenatal Development

4. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Embryo’s Life-Support System Placenta –intertwines but does not join mother and baby Umbilical cord –connects baby to placenta Amnion and amniotic fluid –provides baby’s environment Organogenesis –organ formation The Course of Prenatal Development

5. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Umbilical cord Umbilical arteries Umbilical vein Uterus Maternal portion of placenta Placenta Fetal portion of placenta The Placenta and the Umbilical Cord Fig. 3.2 The Course of Prenatal Development

6. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. The Fetal Period Begins two months after conception; lasts about seven months, until birth Largest prenatal size and weight gains Fingers, toes, skin, features, lungs, other structures, and reflexes all develop to prepare for birth The three trimesters are not the same as the three prenatal periods The Course of Prenatal Development

7. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. The Brain At birth – 100 billion neurons Basic architecture assembled during first two trimesters –Neural tube: first 18–24 days –Neurogenesis –Neuronal migration: 4–6 weeks after conception The Course of Prenatal Development

8. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Nutrition and Weight Gain Nutrition –Need for protein, iron, vitamin D, calcium, phosphorus, magnesium increases 50 percent, water is essential Weight Gain –25 to 35 pounds associated with best reproductive outcomes –Inadequate and excessive weight gain may affect baby birth weight or mother’s health Strategies for Expectant Mothers

9. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Exercise During Pregnancy Decrease duration and intensity as pregnancy progresses Avoid high-risk activities –Warm up, stretch, cool down –Reduce exercise significantly in last four weeks Several studies show exercise during pregnancy not linked to preterm birth Strategies for Expectant Mothers

10. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Prenatal Care Prenatal care varies enormously in –Education –Screening for manageable conditions and treatable diseases –Information on risks and choices before, during, and after pregnancy Good prenatal care makes a difference –Reduces mortality, physical problems later Strategies for Expectant Mothers

11. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Prenatal Care Other countries outside the U.S.: –Have lower rate of low-birth-weight infants –Free or low-cost prenatal and postnatal care –Enjoy liberal paid maternity leave Factors affecting prenatal care in U.S. –Individual and social characteristics –Inadequacy of health care system –Age group differences (adolescents, adults) Strategies for Expectant Mothers

12. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Fig. 3.6 Percentage of U.S. Women Using Timely Prenatal Care: 1990 to 2004

13. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Cultural Beliefs About Pregnancy Conflict between cultural tradition and Western medicine during pregnancy –Food craving satisfaction –Hot-cold theory of illness –Extended family involvement –Stoicism valued by many Asians –Pregnancy as a natural occurrence or a medical condition Strategies for Expectant Mothers

14. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Some General Principles Teratogen –Any agent that causes a birth defect –Severity and type of defect affected by Dose, genetic susceptibility, time of exposure All drugs (prescribed, illegal) can have effects on unborn fetus –Antibiotics, analgesics, asthma medications –1961: thalidomide tragedy Hazards to Prenatal Development

15. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Zygote Embryonic period (wks) Fetal Period (wks) Period of susceptibility to functional defects Fig. 3.7 (modified) 123456789163238 Teratogens and Timing of Their Effects on Prenatal Development Most serious damage from teratogens in first 2–8 weeks Period of susceptibility to structural defects Central nervous system Heart Arms Eyes Legs Ears Teeth Palate External genitalia

16. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Psychoactive Drugs Psychoactive drugs –Act on nervous system and change moods –Alter states of conscious, modify perceptions –Extent of risk and harm varies Use of caffeine, nicotine, and alcohol Fetal alcohol spectrum disorders (FASD) Dangers of second-hand smoke Cocaine and heroin Methamphetamine and marijuana Hazards to Prenatal Development

17. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Incompatible Blood Types Poses risk to prenatal development –Between mother and father –Between mother and baby –Blood groups (A, B, O, AB) –Rh factor (positive, negative) –Vaccine within 3 days of birth Hazards to Prenatal Development

18. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Environmental Hazards Father’s exposure to lead, radiation X-ray radiation Pollutants and toxin wastes Fertilizers and pesticides Lead-based paints Petrochemicals Hazards to Prenatal Development

19. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Maternal Diseases Diseases and infections cross the placenta barrier –Rubella (German measles) –Diabetes Sexually transmitted infections –Syphilis, Genital herpes –AIDS, HIV infection New medications and vaccines available Hazards to Prenatal Development

20. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Other Parental Factors Maternal diet, nutrition, and weight –Folic acid and iron –Fish: PCBs and mercury levels Maternal age –Highest risks: adolescents, over 35 years –Down syndrome Maternal emotional states Hazards to Prenatal Development

21. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. Other Parental Factors Paternal factors –Father’s diet and low vitamin C –Drug use effects on sperm –Smoking – effects of second-hand smoke –Father’s age at conception Birth defects: dwarfism, Marfan’s Syndrome Hazards to Prenatal Development

22. © 2010 The McGraw-Hill Companies, Inc. All rights reserved. The End 3