Chapter 2 From Conception to Birth Berger 5e Students

FROM CONCEPTION TO BIRTH

Chapter Overview

• Overview of the chapter topics:

  • The beginnings: From conception to birth.

  • Important terms to know.

  • Development from zygote to newborn.

  • Birth process.

  • Formation of a new family.

In the Beginning (Part 1)

• Humans as a species share a remarkable genetic similarity.

• Each individual is unique, with distinct characteristics.

In the Beginning (Part 2)

• Chromosome and Gene Information:

  • Humans possess approximately 21,000 genes on 46 chromosomes arranged in pairs.

  • Out of these, 22 chromosome pairs are closely matched; the 23rd pair determines sex (XX for females, XY for males).

In the Beginning (Part 3)

• Gametes:

  • Reproductive cells, sperm (male) and ova (female).

  • Each gamete contains 23 chromosomes.

  • Zygote: Formed when an ovum and sperm combine, resulting in a total of 46 chromosomes (23 from each parent).

Important Terms to Know (Part 4)

• Definitions of key genetic terms:

  • Genome: Complete set of genetic instructions.

  • Allele: Different versions or forms of a gene.

  • Genotype: An organism's genetic makeup or potential.

  • Phenotype: Observable characteristics resulting from genotype.

Genetic Interactions (Part 5)

• Copy Number Variations:

  • Involves genes with repeated or deleted base pairs; more common than single-gene variations.

• Dominant and Recessive Genes:

  • Dominant genes have a more significant impact on phenotype than recessive genes.

  • Dominant genes can mask the traits of recessive genes.

• X-linked genes:

  • Special variant of the dominant-recessive inheritance pattern.

Twins (Part 6)

• Types of twins:

  • Monozygotic (Identical) twins: Form from one zygote that splits early in development.

  • Dizygotic (Fraternal) twins: Result from two separate ova fertilized by two different sperm.

FROM ZYGOTE TO NEWBORN

Development Stages (Part 1)

• Three main periods of prenatal development:

  • Germinal period: First 14 days after conception.

  • Embryonic period: Third to eighth week of development.

  • Fetal period: Ninth week until birth.

Germinal Period (Part 2)

• First 14 days post-conception:

  • Begins with zygote duplication.

  • Placenta development and implantation occur (around 10 days).

Embryonic Period (Part 3)

• By third to eighth week:

  • Formation of the neural tube, critical for brain and spine development.

  • Early features such as head shape and facial structures develop.

  • Heart starts to beat and limbs begin to separate.

Fetal Period (Part 4)

• From ninth week to birth:

  • Genital formation and the influence of sex hormones on brain development.

  • Significant brain growth occurs during the fourth to sixth months.

  • By three months, the fetus weighs about 3 ounces.

Age of Viability (Part 6)

• Defined as the point at which a preterm newborn could survive outside the womb with medical assistance:

  • Approximately 22 weeks post-conception.

  • At this stage, the brain can regulate essential body functions, such as breathing.

Survival Rates (Part 7)

• Survival statistics during developmental periods:

  • Germinal Period: 65% don't survive.

  • Embryonic Period: 20% aborted spontaneously.

  • Fetal Period: 5% suffer spontaneous abortion before viability.

  • Birth: Roughly 27% of zygotes develop into living newborns.

PROBLEMS AND SOLUTIONS

Chromosomal and Genetic Problems (Part 1)

• Most people (92%) don’t have serious genetic conditions.

• Up to half of zygotes may have abnormal chromosome numbers leading to spontaneous abortion.

• 99% of newborns have a complete set of 46 chromosomes.

Genetic Syndromes (Part 2)

• Some conditions related to trisomy (additional chromosome):

  • Patau syndrome: 1 in 10,000 births.

  • Edwards syndrome: 1 in 5,000 births.

  • Down syndrome: 1 in 700 births.

Problems of the 23rd Pair (Part 3)

• Genetic issues affecting sex chromosomes:

  • Infants born with atypical numbers of sex chromosomes may face cognitive and fertility issues.

Gene Disorders (Part 4)

• Common gene disorders:

  • Recessive disorders: Early-onset Alzheimer’s, muscular dystrophies, Marfan syndrome, Huntington’s chorea.

  • X-linked recessive conditions: Hemophilia, Duchenne muscular dystrophy, Fragile-X syndrome.

  • Common genetic disorders: Sickle-cell disease, cystic fibrosis.

Genetic Complexity (Part 5)

• Major human traits typically arise from multiple genes,

  • Some genes may be beneficial while others can lead to conditions like anxiety.

Genetic Counseling (Part 6)

• Provides guidance to prospective parents about genetic risks.

• Importance of excellent communication skills.

Teratogens (Part 7)

• Agents causing prenatal abnormalities include:

  • Viruses, chemicals, drugs, chronic stress.

  • Damage can occur during critical exposure periods.

• Fetal alcohol syndrome (FAS): Consequences of alcohol exposure during pregnancy.

Genetic Vulnerability (Part 8)

• Some zygotes inherit genes making them more susceptible to teratogens,

  • Male fetuses show higher vulnerability to such agents.

Low Birthweight (Part 9)

• Defined categories:

  • Low birthweight (LBW): Under 5½ pounds.

  • Very low birthweight (VLBW): Under 3 pounds 5 ounces.

  • Extremely low birthweight (ELBW): Under 2 pounds 3 ounces.

Consequences of LBW (Part 10)

• Risks associated with low birthweight include:

  • Developmental delays and increased impairment rates.

  • Long-term effects manifesting in smaller brain volumes and lower IQ in childhood.

BIRTH AND THE NEW FAMILY

Birth Process (Part 1)

• Labor initiation:

  • Triggered by signals from the fetal brain causing uterine contractions.

  • Average duration for first births: 12 hours; later births: around 7 hours.

• Stages of labor:

  • Stage 1: Early and active labor.

  • Stage 2: Delivery.

  • Stage 3: Afterbirth.

Birth Options (Part 2)

• Delivery settings:

  • Variations exist between nations and localities.

  • Common settings: Hospitals, homes, birthing centers, midwives, and doulas.

Risks and Benefits of Birth Settings (Part 3)

• Risks associated with non-hospital births:

  • Potential for higher infant mortality and lack of insurance coverage.

• Benefits:

  • Typically lower costs and reduced medical interventions.

Cesarean Section (C-section) (Part 4)

• Advantages:

  • Quick removal of fetus, scheduled births.

• Disadvantages:

  • Potential issues with breastfeeding and higher risks of medical complications in infants.

Newborn Assessment (Part 5)

• Apgar scale: Measures newborn health on a scale from 0-10; below 5 indicates emergency.

  • Components: Appearance, Pulse, Grimace, Activity, Respiration.

• Brazelton Neonatal Behavioral Assessment:

  • Assesses newborn responsiveness, tracking 46 behaviors and 20 reflexes.

The New Family (Part 1)

• Significance of bonding:

  • Importance of early contact, cross-fostering, and kangaroo care.

• Potential problems for mothers:

  • Physical and psychological challenges including baby blues and postpartum depression.

Family Dynamics (Part 2)

• Role of fathers and support systems:

  • Importance of paternal involvement in maternal health and stress management for fetal well-being.