© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 1 John W. Santrock Prenatal Development 4

© 2007 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 Expectant Parents’ Experiences Like During Prenatal Development? What Are Some Potential Hazards to Prenatal Development?What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 6 Parts of the Embryo Endoderm: inner layer of cells forming digestive and respiratory systems Ectoderm: outermost layer of cells forming nervous system, sensory receptors, and skin parts What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 7 Parts of the Embryo Mesoderm: middle layer of cells forming circulatory system, bones, muscles, excretory and reproductive systems What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 8 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 9 The Placenta and the Umbilical Cord What Is the Course of Prenatal Development? Umbilical cord Umbilical arteries Umbilical vein Uterus Maternal portion of placenta Placenta Fetal portion of placenta Fig. 4.1

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 10 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 11 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 What Is the Course of Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 12 Conception to 4 wks 8 weeks 12 weeks 16 weeks 20 weeks 24 weeks 28 weeks 32 weeks 36 to 38 weeks Less than 1/10th of an inch long Less than 1 inch long About inches long, weighs 4 to 5 pounds 19 inches long, weighs 6 pounds About 5.5 inches long, weighs about 4 ounces About inches long, weighs 1/2 to 1 pound About inches long, weighs 1 to 1.5 pounds About inches long, weighs 2.5 to 3 pounds About 3 inches long, weighs about 1 ounce Third trimester begins Second trimester begins First trimester begins The three trimesters of prenatal development

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. 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 What Are Expectant Parents’ Experiences Like During Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 14 Early Signs and Symptoms of Pregnancy What Are Expectant Parents’ Experiences Like During Prenatal Development? Fig. 4.4

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 15 Three Trimesters and Preparation for Birth Third trimester Second trimester First trimester Anticipates end; uterus expands to point below breastbone Less fatigue and nausea; uterus expands into abdominal cavity Very tired; nausea and pregnancy sickness; breasts change; emotional changes What Are Expectant Parents’ Experiences Like During Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. 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 What Are Expectant Parents’ Experiences Like During Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 17 Expectant Mother’s 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 What Are Expectant Parents’ Experiences Like During Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 18 Expectant Mother’s Nutrition and Weight Gain Weight Gain –Maternal obesity adversely impacts pregnancy outcomes; carries risks Hypertension Diabetes Respiratory complications Infections What Are Expectant Parents’ Experiences Like During Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 19 Exercise During Pregnancy Exercise for shorter time intervals Decrease intensity as pregnancy progresses Avoid prolonged overheating Avoid high-risk activities What Are Expectant Parents’ Experiences Like During Prenatal Development? 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

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 20 Some General Principles Teratogen –Any agent that causes a birth defect –Only about half of potential effects appear at birth Severity and type of defect affected by –Dose –Genetic susceptibility –Time of exposure What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 21 Prescription and Nonprescription Drugs What Are Some Potential Hazards to Prenatal Development? Damage discovered after a cluster of deformed babies is born – Specific antibiotics – Some antidepressants – Certain hormones – Diet pills – Aspirin – Caffeine

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 22 Zygote Embryonic period (wks) Fetal Period (wks) Period of susceptibility to functional defects Fig. 4.7 (modified) Terogens 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

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 23 Psychoactive Drugs Psychoactive drugs –Act on nervous system –Alter states of conscious –Modify perceptions –Change moods What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 24 Psychoactive Drugs Alcohol –Fetal alcohol syndrome (FAS) Nicotine Cocaine Marijuana Methamphetamine Heroin What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 25 Environmental Hazards Fathers’ exposure to lead and radiation Certain pesticides Petrochemicals Environmental pollutants and toxins Toxic waste Manufactured chemicals What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 26 Infectious Diseases Rubella Sexually transmitted infections –Syphilis –Genital herpes –AIDS, HIV infection What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 27 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 What Are Some Potential Hazards to Prenatal Development?

© 2007 The McGraw-Hill Companies, Inc. All rights reserved. Slide 28 Other Parental Factors Maternal nutrition and low birthweight Obesity during pregnancy Maternal age—too young, too old Paternal age and risks Emotional states and stress Maternal hormonal treatments What Are Some Potential Hazards to Prenatal Development?