Janet Belsky’s Experiencing the Lifespan, 3e Chapter 2: Prenatal Development, Pregnancy, and Birth Meredyth Fellows, West Chester University of PA

Fertilization: The Reproductive Systems Female Reproductive Structures Uterus Endometrium Cervix (neck of uterus) Fallopian tubes Ovaries Ova reside here Ova contain mother’s genetic material

Reproductive Systems Male Reproductive Structures Testes (continually manufacture sperm) Penis

Process of Fertilization: Union of Sperm and Egg Ovulation occurs: ovum expelled from ovary suctioned into fallopian tube Millions of sperm travel up fallopian tube to ovum Fertilization One sperm penetrates the ovum. Nuclei (genetic material) of the male and female cells combine.

Genetics: Chromosomes, DNA, Genes Located in the nucleus of every cell, a threadlike strand of DNA, which carries the genes that transmit genetic information DNA (deoxyribonucleic acid) Material that makes up genes, which bear our hereditary characteristics Gene A segment of DNA that contains a chemical blueprint for manufacturing a particular protein

Genetics: Chromosomes, DNA, Genes 23 chromosome pairs contain DNA (genetic material) 23 single strands each from mother and father Sex chromosome = 1 chromosome pair (XX female, XY male) KARYOTYPE

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

Germinal Stage, first two weeks: from zygote to blastocyst Zygote (fertilized ovum) In the first 36 hours, zygote divides once Divides again every 12-15 hours Travels down fallopian tube for 3 days Once in the uterus, differentiates into layers— zygote is identified as a blastocyst and has roughly 100 cells Blastocyst implants into the upper part of the uterus Blood vessels proliferate to form the placenta BLASTOCYST

Embryonic Stage: Weeks 3 to 8 Fast paced; all major organs constructed 3rd week, circulatory system forms and heart beats 20 to 24 days neural tube forms—differentiates into brain and spinal cord Day 26, arm buds form Day 27, leg buds 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.

Principles of Prenatal Development 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.

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

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 neural tube, reach their staging area, and begin to differentiate. Climbing Neurons

Fetal Stage Age of viability is 22 weeks (earliest date for possibility of survival). Vital that baby’s lungs are mature enough to breathe in oxygen and to expel carbon dioxide. By the 25th week, viability is above 50% if acute care is available. Birth weight is important to health of baby. Baby needs as much time in the womb as possible. During the last 2 months, fetus gains almost 5 pounds.

Poised to Be Born! Fetus positioned in the womb late in pregnancy. Notice the placenta, amniotic sac, and umbilical cord.

Pregnancy Gestation Period: 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. Progesterone; human chorionic gonadotropin (HCG) Miscarriages (spontaneous abortions) more prevalent at this time: Roughly 1 in 10 pregnancies ends in miscarriage. Miscarriage rate increases to 1 in 5 for women in their late thirties.

Pregnancy: Second Trimester Physically may feel much better By week 14, uterus grows (maternity clothes!) Quickening occurs (first indication of movement of the fetus) Feelings of attachment may begin A strong sense of attachment during pregnancy predicts positive bonding after birth.

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

Pregnancy Is Not a Solo Act Forces that may contribute the experience of distress during pregnancy Economic concerns; low SES places women at risk of feeling demoralized and depressed possible lack of access to prenatal care, proper foods, and often, social support Positive forces Presence of a loving partner may predict a happy pregnancy. The perception of being cared about and loved; a sense of connectedness Husbands also may experience strong emotions. May feel concerned about this life change Social support necessary

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

Basic Teratogenic Principles 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, depending on fetal and maternal vulnerabilities Teratogens may also exert influence long after exposure. DES, diethylstilbestrol Learning disabilities

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

Measurement Issues: How much exposure is too much? Researchers experience difficulty defining exact amounts of exposure that may cause harm to the developing organism. Self-report questionnaires may be unreliable. Rule of thumb: Don’t smoke, drink, take drugs, and avoid exposure to teratogens.

In Focus: Pregnancy as a Programmer of Adult Life Fetal Programming Research New research discipline Explores the impact of traumatic pregnancy events and intense stress on producing low birth weight, obesity, and long-term physical problems. The “Hunger Winter” in 1944, Holland Findings: Heart disease rates were higher if a fetus was exposed to the Hunger Winter.

Threats from Within: Chromosomal Disorders Chromosomes: human complement is 46 (23 pairs) Embryo may miscarry if developing baby is missing or has an extra chromosome. e.g., Down syndrome – trisomy 21 Nondisjunction (cell division error in egg or sperm) Causes an extra chromosome or piece of that copy to adhere to chromosome pair 21 Born with 47 chromosomes

Chromosomal Disorders: Down Syndrome − Trisomy 21 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

Down Syndrome continued Risk for heart defects and childhood leukemia Mild to moderate mental retardation Shortened lifespan Average life expectancy, 58!

Genetic Disorders: Single-Gene Disorders 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 disorders Recessive disorders Sex-linked single-gene disorders

Genetic Disorders Dominant disorders Recessive 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.

Genetic Disorders: Sex-linked single-gene disorders 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

Interventions: Sorting out the Options First Step: Genetic Counselor Counsels couples about their own or their children’s risk of developing genetic disorders Advice about available treatments Goal: permit couples to make mutual decision Genetic Testing Blood test: determines whether a person carries the gene for a genetic disorder

Prenatal Tests Ultrasound Chorionic Villus Sampling Commonly used to date the pregnancy and chart the fetus’s growth, but it can also reveal structural abnormalities. Chorionic Villus Sampling During 1st trimester, remove piece of developing placenta Test for genetic and chromosomal conditions Risks: 5% risk of miscarriage Chance of limb impairment

Prenatal Testing Amniocentesis 2nd trimester procedure, typically week 14 Remove cells from amniotic fluid and test for genetic and chromosomal conditions Risk Miscarriage

Infertility The inability to conceive after a year of unprotected sex (includes inability to carry a child to term) Infertility rates higher at older ages Male and female problems equally involved

Interventions: Assisted Reproductive Technology ART: treatment in which the egg is fertilized outside of the womb In Vitro Fertilization After woman has been given fertility drugs, eggs are harvested and put into Petri dish along with her partner’s sperm. Developing cell mass is inserted into the woman’s uterus with the hope of implantation into the uterine wall.

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

Birth Options 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 Section Procedure common in some countries Used in the United States if complications occur

Medical Interventions Episiotomy Epidural Electronic Fetal Monitor Cesarean Section (C-Section) Remove fetus manually by making incision into abdominal wall and uterus Used when complications occur

The Newborn Apgar Scale: first test immediately after birth Rated 0 to 2 for each category at 1 minute and 5 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 (neonatal intensive care unit)

Threats to Development Low birth weight (LBW) Body weight of less than 5½ lbs. Arrived too early or did not grow in womb Very low birth weight Body weight of less than 3¼ lbs. Often very premature and rushed to NICU

Infant Mortality: death during first year of life Varying mortality rates among countries Notice difference between developing and developed countries Deaths of children under 1 year of age in 2011