Slide 1 3 Prenatal Development John W. Santrock © 2009 The McGraw-Hill Companies, Inc. All rights reserved. Slide 2 Prenatal Development • What Is the Course of Prenatal Development? • What Are Expectant Parents’ Experiences Like During Prenatal Development? • What Are Some Potential Hazards to Prenatal Development? © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 3 The Germinal Period • First two weeks after conception – Creation of zygote – Continued cell division – Attachment of zygote to uterine wall – Differentiation of cells has begun © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 4 Parts of the Zygote • Blastocyst: inner layer of cells that develops during the germinal period – Later develops into embryo • Trophoblast: outer layer of cells that develops during germinal period – Provides embryo nutrition and support © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 5 The Embryonic Period • Two to eight weeks after conception – Rate of cell differentiation intensifies – Support systems for cells form – Organogenesis: organ formation – Embryo has three layers of cells © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 6 Parts of the Embryo • Endoderm: inner layer of cells form digestive and respiratory systems • Ectoderm: outermost layer of cells form skin parts, nervous system, and sensory receptors • Mesoderm: middle layer of cells form bones, circulatory system, muscles, excretory and reproductive systems © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 7 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 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 8 The Placenta and the Umbilical Cord Uterus Umbilical cord Placenta Fig. 3.2 Umbilical vein Umbilical arteries Fetal portion of placenta Maternal portion of placenta © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 9 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 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 10 The Fetal Period • The three trimesters are not same as the three prenatal periods • At birth, average baby weighs 7.5 pounds and is about 20 inches long © 2009 The McGraw-Hill Companies, Inc. All rights reserved. Third trimester begins About 16.518 inches long, weighs 4 to 5 pounds 32 weeks About 14-17 inches long, weighs 2.5 to 3 pounds 19 inches long, weighs 6 pounds Less than 1/10th of an inch long About 11-14 inches long, weighs 1 to 1.5 pounds About 10-12 inches long, weighs 1/2 to 1 pound Fig. 3.3 First trimester begins Slide 11 The three trimesters of prenatal development Less than 1 inch long About 5.5 inches long, weighs about 4 ounces About 3 inches long, weighs about 1 ounce Second trimester begins © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Is the Course of Prenatal Development? Slide 12 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 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 13 Confirming the Pregnancy and Calculating the Due Date • Pregnancy test checks for human chorionic gonadotropin (HCG) • Pregnancy calculated from first day of the woman’s last menstrual period – Lasts about 280 days or 40 weeks • Fetal life begins at ovum fertilization © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 14 Early Signs and Symptoms of Pregnancy © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 15 Three Trimesters and Preparation for Birth First trimester Very tired; nausea and pregnancy sickness; breasts change; emotional changes Second trimester Less fatigue and nausea; uterus expands into abdominal cavity Third trimester Anticipates end; uterus expands to point below breastbone © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 16 Preparation for the Baby’s Birth • Braxton Hicks contractions increase • Cervix becomes softer and thinner • Awkwardness • Fatigue and desire for pregnancy to end • Nesting urge and spurts of energy © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 17 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 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 18 Exercise During Pregnancy • Exercise for shorter time intervals • Decrease intensity as pregnancy progresses • Avoid prolonged overheating • Avoid high-risk activities • Warm up, stretch, cool down • After exercise, lie on left side 10 minutes • Wear supportive shoes and bra • Reduce exercise significantly in the last four weeks © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 19 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 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 20 Prenatal Care • Other countries outside the U.S.: – Have lower rate of low-birth-weight infants – Receive free or low-cost prenatal and postnatal care – Enjoy liberal paid maternity leave © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 21 Prenatal Care • Factors affecting prenatal care in U.S. – Individual and social characteristics • Undesired pregnancy – Inadequacy of health care system – Ethnic group differences – Age group differences (adolescents, adults) © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 22 Cultural Beliefs About Pregnancy • • • • • Satisfying ‘questionable’ food cravings ‘Hot-cold’ theory of illness Role of extended family Stoicism in Asian cultures Pregnancy as a natural occurrence or a medical condition © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 23 Cultural Beliefs About Pregnancy • Latino cultures in U.S. – Less use of family planning services than other Americans – Beliefs about contraceptives – Seek advice of older women and mothers – Use of curanderos – Undocumented illegals wait much longer © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Expectant Parents’ Experiences Like During Prenatal Development? Slide 24 Cultural Beliefs About Pregnancy • Asian cultures in U.S. – Chinese expectant mothers’ behaviors linked to character formed in the womb • • • • Listening to classical music linked to patience Charitable behavior linked to morality Avoid dishonest people Dispel negative thoughts and feelings © 2009 The McGraw-Hill Companies, Inc. All rights reserved. Slide 25 © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 26 Some General Principles • Teratogen – Any agent that causes a birth defect – About half of potential effects appear at birth • Severity and type of defect affected by – Dose – Genetic susceptibility – Time of exposure © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 27 Prescription and Nonprescription Drugs • Prescriptions given during pregnancy – Antibiotics, analgesics, asthma medications – 1961: thalidomide tragedy • All drugs (prescribed, illegal) can have effects on unborn fetus © 2009 The McGraw-Hill Companies, Inc. All rights reserved. Teratogens and Timing of Their Effects on Prenatal Development Slide 28 Zygote 1 2 Embryonic period (wks) Fetal Period (wks) 3 4 5 6 7 8 9 16 32 38 Central nervous system Most Heart serious Arms damage Eyes from teratogens Legs in first 2–8 Ears weeks Teeth Period of susceptibility Palate to structural defects External genitalia Period of susceptibility to functional defects Fig. 3.8 (modified) © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 29 Psychoactive Drugs • Psychoactive drugs – Act on nervous system and change moods – Alter states of conscious and modify perceptions – Extent of risk and harm varies © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 30 Psychoactive Drugs • • • • Caffeine and nicotine Alcohol – Fetal Alcohol Syndrome (FAS) Cocaine and heroin Methamphetamine and marijuana © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 31 Incompatible Blood Types • Between mother and father • Between mother and baby – Blood group (A, B, O, AB) – Rh factor (positive, negative) – Vaccine within 3 days of birth © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 32 Environmental Hazards • • • • • • Father’s exposure to lead, radiation X-ray radiation Pollutants and toxin wastes Fertilizers and pesticides Lead-based paints Petrochemicals © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 33 Maternal Diseases • Diseases and infections cross the placenta barrier – Rubella – Diabetes • Sexually transmitted infections – Syphilis – Genital herpes – AIDS, HIV infection © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 34 Other Maternal Factors • Maternal diet and nutrition – Folic acid and iron – Fish: PCBs and mercury levels • Maternal age – Highest risks: adolescents, over 35 years • Maternal emotional states © 2009 The McGraw-Hill Companies, Inc. All rights reserved. What Are Some Potential Hazards to Prenatal Development? Slide 35 Other Paternal Factors • Father’s diet and low vitamin C • Drug use effects on sperm • Smoking during pregnancy – effects of second-hand smoke • Father’s age at conception © 2009 The McGraw-Hill Companies, Inc. All rights reserved. Slide 36 3 The End © 2009 The McGraw-Hill Companies, Inc. All rights reserved.