Experiencing the Lifespan

1. Experiencing the Lifespan Chapter 2: Prenatal Development, Pregnancy, and Birth

2. Proximodistal Growth from middle to outside Cephalocaudal Growth from head to tail (feet) Mass to Specific Large structures appear before finer details Large movements appear before finer movements Principles of Prenatal Development

3. Germinal First 14 days Period of Zygote Embryonic Week 3 to 8 Period of Embryo Fetal Week 9 to Birth Period of Fetus Stages of Prenatal Development

4. Day 1 to 14, time from fertilization to implantation of blastocyst Zygote divides once in the first 36 hours Every 12 - 15 hours, divides again 3 day trip down fallopian tube Once in the uterus, differentiates into layers Zygote now called a blastocyst and has about 100 cells Blastocyst implants into the upper part of the uterus Blood vessels proliferate to form the placenta Germinal Stage: First two weeks

5. Recap: Events of the Germinal Stage

6. Fast paced forming of major organs and body structures 3rd week after fertilization, circulatory system forms and heart beats Neural tube forms�begins to differentiate into the brain and spinal cord Arm and leg buds appear and elongate, the heart begins to pump Outlines of eyes and ears appear Feet, elbows, wrists and fingers begin to appear By week 8, the embryo is 1.5 inches long. The internal organs are in place and embryo begins to look human. Embryonic Stage: Weeks 3 to 8

7. Note proximodistal and cephalocaudal trends Weeks 3, 4, and 9 of Embryonic Stage

8. Fetal Stage: Week 9 to Birth Baby grows dramatically; body structures are refined; building blocks of the brain are fully assembled Neurons ascend to the top of the tube, reach their staging area and begin to differentiate ( see illustration)

9. Age of viability 22 weeks (earliest date for survival) Vital that baby�s lungs are mature enough to breathe in oxygen and expel carbon dioxide. By the 25th week, viability is above 50% if acute care is available. Birth weight important to health of baby Baby needs as much time in womb as possible During last two months fetus gains 5 pounds Fetal Stage

10. Gestation Period: period of pregnancy, 267-277 days Divided into Trimesters (about 3 months each) Important! Each woman may vary in her experience (physical and emotional) of pregnancy. First Trimester Following implantation of blastocyst into uterus, flood of hormones may produce fainting, headaches, fatigue, tender breasts and morning sickness Miscarriages (spontaneous abortions) are more prevalent at this time Roughly 1 in 10 pregnancies ends in miscarriage Women in their late 30�s, miscarriage rate increases to 1 in 5 Pregnancy

11. Physically may feel much better Need for maternity clothes Quickening occurs (first indication of the fetus moving) Feelings of attachment may begin A strong sense of attachment predicts positive bonding after birth (although attachment can happen at any time!) Pregnancy: Second Trimester

12. Physical Symptoms and Emotional States Leg cramps, backaches, anxiety, numbness in lower limbs, heartburn, insomnia Irregular uterine contractions as baby sinks into the birth canal Anxiety may begin as the focus shifts while awaiting birth Pregnancy: Third Trimester

13. Threats to the Developing Baby: Category 1: Teratogens Teratogens: substances that may cross the placenta to harm the developing embryo or fetus Examples: Medications � Thalidomide Diseases � Rubella Social Drugs - Alcohol, Nicotine, Cocaine Environment- Pesticides, Radiation Stress � hormones and effects on unborn baby

14. Teratogens do most damage during sensitive periods. Four Principles Most likely to cause structural damage during embryonic period Can affect developing brain throughout pregnancy 2nd and 3rd trimester: risk of developmental disorders Operate in a dose-response fashion (threshold level) Exert damage unpredictably Teratogens may also exert influence long after exposure (e.g. DES, diethylstilbestrol) Basic Teratogenic Principles

15. Teratogens: Nicotine and Alcohol Nicotine: Constricts blood vessels Increases risk of smaller than normal and less healthy newborn Alcohol: Excessive consumption contributes to chance of Fetal Alcohol Syndrome

16. Birth! Stage 1: Dilation and Effacement Stage 2: Birth Stage 3: The Expulsion of the Placenta Some threats during birth include: baby in breech position, cervix not fully dilating, difficult position of umbilical cord

17. Birth options and Providers: Natural childbirth Deliver without medication with the help of midwife or doula. Lamaze (pain management) Bradley (natural, non-medicated childbirth) Sometimes, medical intervention is needed. Cesarean Procedure common in some countries Used in the U.S. if complications occur Birth Options

18. Cesarean Section (C-Section) Remove fetus manually by making incision into abdominal wall and uterus Used when complications occur Medical Interventions

19. Low Birth Weight (LBW) Body weight of less than 5 � lbs. Arrived too early or did not grow in womb Very low birth weight Body weight of less than 3 � lbs. Often very premature and rushed to NICU (neonatal intensive care unit) Threats to Development

20. Infant Mortality Infant mortality is an overall barometer of a nation�s status. Countries vary greatly in their infant mortality rates�with developing countries doing far worse. The U.S. ranks a humiliating 41st in the world. One reason is our nation�s high income inequalities, and inadequate access to good prenatal care SOCIOECONOMIC STATUS AFFECTS OUR LIFESPAN JOURNEY FROM the FIRST MOMENTS OF LIFE.

21. Threats from Within: Chromosomal Disorders Chromosomes: human complement is 46 (23 pairs) If developing baby is missing or has an extra chromosome, embryo may miscarry When an extra chromosome does occur: Down syndrome � trisomy 21 (extra chromosome or piece copy to adhere to chromosome 21)

22. Apgar Scale: first test immediately after birth Rated 0 to 2 for each category at one minute and five minutes after birth Color Muscle Tone Respiration Heart Rate Reflex Response Score over 7 healthy Under 7, must be monitored or resuscitated and may go to NICU The Newborn

23. Risk factors: advanced maternal and paternal age (in women, ova may have chromosomal faults) Women over 40, 1 in 100 Women over 45, 1 in 25 Symptoms: distinctive physical characteristics Flat facial profile Upward slant to eyes Stocky appearance Enlarged tongue Chromosomal Disorders: Down Syndrome_Trisomy 21

24. At risk for heart defects and childhood leukemia Mild to moderate mental retardation Shortened life-span Average life expectancy, 58! Down Syndrome continued

25. Genes come in pairs � one on each chromosome � and determine specific traits While most traits are dependent on many genes, single gene disorders occur due to a flaw in a particular gene. Three modes of inheritance: Dominant Recessive Sex-Linked Genetic Disorders: Single-Gene Disorders

26. Genetic Disorders Dominant disorders A person who inherits one copy of the gene always gets the disease. If one parent has the genetic disease, each child has a 50/50 chance of inheriting the disease. Recessive Child gets illness by inheriting two copies of the abnormal gene that causes the disorder Odds of baby born to two carriers having the illness are 1 in 4.

27. Genetic Disorders: Sex-linked single-gene disorders Sex-Linked single- gene disorder Illness carried on the mother�s X chromosome Typically leaves the female offspring unaffected but has a 50/50 chance of striking each male child