Study Notes on Prenatal Development and Birth CH3

Chapter 3: Prenatal Development and Birth

Outline of the Chapter

  1. Prenatal Development

  2. Birth

  3. The Postpartum Period

Prenatal Development

Topics

  • The course of prenatal development.

  • Teratology and hazards to prenatal development.

  • Prenatal care.

  • Normal prenatal development.

The Course of Prenatal Development
1. The Germinal Period

  • Duration: The germinal period lasts the first two weeks after conception.

  • Key Stages:

    • Creation of the zygote.

    • Continued cell division.

    • Attachment of the zygote to the uterine wall.

  • Definitions:

    • Blastocyst: The inner layer of cells that develops into the embryo.

    • Trophoblast: The outer layer of cells that provides nutrition and support for the embryo.

2. The Embryonic Period

  • Duration: Lasts from two to eight weeks post-conception.

  • Characteristics:

    • Intensified rate of cell differentiation.

    • The mass of cells develops into an embryo.

  • Three Cell Layers:

    • Endoderm: Inner layer.

    • Mesoderm: Middle layer.

    • Ectoderm: Outer layer.

  • Development Conditions: Life-support systems for embryo form; vital organs begin to appear.

3. Key Structures Formed

  • Amnion: A sac containing clear fluid in which the embryo floats.

  • Umbilical Cord: Contains two arteries and one vein connecting the baby to the placenta.

  • Placenta: A disk-shaped organ where small blood vessels from the mother and fetus intertwine.

  • Organogenesis: The formation of organs takes place during the first two months of prenatal development.

4. The Fetal Period

  • Duration: Lasts about seven months from two months post-conception to birth.

  • Average Birth Statistics: At birth, an average American baby weighs 8 pounds and is about 20 inches long.

  • Trimesters: Prenatal development is divided into three trimesters of three months each, though these differ from the germinal, embryonic, and fetal periods.

Development During Trimesters
1. The First Trimester

  • Conception to 4 weeks:

    • Length: less than 1/10 inch.

    • Initial development of spinal cord, nervous system, gastrointestinal system, heart, and lungs.

    • Amniotic sac envelops the tissue.

    • Called a "zygote".

  • At 8 weeks:

    • Length: just over 1 inch.

    • Formation of face with rudimentary eyes, ears, mouth, and tooth buds.

    • Movement of arms and legs begins; fetal heartbeat detectable via ultrasound.

    • Referred to as an "embryo".

  • At 12 weeks:

    • Length: about 3 inches and weight: about 1 ounce.

    • Movements: arms and legs, distinct fingerprints, facial expressions form (smile, frown, suck, swallow).

    • Sex distinguishable.

    • Referred to as a "fetus".

2. The Second Trimester

  • At 16 weeks:

    • Length: about 6 inches, weight: 4-7 ounces.

    • Strong heartbeat; thin, transparent skin; downy hair (lanugo).

    • Finger and toenails begin forming; coordinated movements observed.

  • At 20 weeks:

    • Length: about 12 inches, weight: close to 1 pound.

    • Heartbeat audible; sucking thumb and hiccuping behavior; presence of hair, eyelashes, and eyebrows.

  • At 24 weeks:

    • Length: about 14 inches, weight: 1-1.5 pounds.

    • Wrinkled skin with protective vernix caseosa covering; eyes are open; waste begins to collect in bowel; strong grip noted.

3. The Third Trimester

  • At 28 weeks:

    • Length: about 16 inches, weight: about 3 pounds.

    • Development of body fat; very active; rudimentary breathing movements present.

  • At 32 weeks:

    • Length: 16.5 to 18 inches, weight: 4 to 5 pounds.

    • Periods of sleep and wakefulness present; responsiveness to sounds; may assume birth position; head bones are soft and flexible; iron storage in liver.

  • At 36 to 38 weeks:

    • Length: 19 to 20 inches, weight: 6 to 7.5 pounds.

    • Skin appears less wrinkled, increased thickness of vernix caseosa, reduced lanugo, decreased activity level, and gaining of immunities from the mother.

Brain Development

  • Babies are born with approximately 20 to 100 billion neurons, which are responsible for information processing at the cellular level.

  • Phases of Brain Development:

    1. Neural Tube Formation: Develops around 18-24 days post-conception; failure to close leads to defects like anencephaly and spina bifida.

    2. Neurogenesis: High proliferation of new immature neurons, starting around week 5.

    3. Neuronal Migration: Cells move outward to their appropriate locations between weeks 6 and 24.

    4. Neural Connectivity: Initiated around the 23rd week, connections between neurons begin to form.

Teratology and Hazards to Prenatal Development
1. Teratogen

  • Defined as any agent that can cause a birth defect or negatively affect cognitive and behavioral development outcomes.

  • Teratology: The study of the causes of birth defects.

  • Factors Influencing Severity:

    • Dose: the amount of exposure to the teratogen.

    • Genetic Susceptibility: the genetic disposition of the organism.

    • Timing: the stage of development during which exposure occurs.

2. Negative Effects of Exposure During Fetal Period

  • Possible outcomes include:

    • Stunted growth.

    • Issues in fetal brain development.

    • Complications in organ functioning.

3. Drug Interactions

  • Certain prescription and nonprescription drugs can act as teratogens, such as:

    • Antibiotics (e.g., streptomycin, tetracycline).

    • Some antidepressants.

    • Hormones (e.g., progestin, synthetic estrogen).

    • Accutane, used for acne treatment.

4. Effects of Psychoactive Drugs

  • Mental health drugs affecting consciousness and mood.

    • Examples include caffeine (linked to lower birth weight), alcohol (leading to fetal alcohol spectrum disorders - FASD), nicotine (associated with low birth weight and ADHD), cocaine (linked to neurological issues), marijuana (lower intelligence and birth weight), and heroin (behavioral difficulties at birth).

5. Environmental Hazards

  • Include exposure to radiation and chemical pollutants which can impact fetal development.

6. Maternal Diseases

  • Diseases such as rubella, syphilis, genital herpes, HIV/AIDS, and diabetes can affect fetal development adversely.

7. Other Parental Factors

  • Maternal diet and nutrition (e.g., lack of folic acid; mercury-laden fish), maternal obesity, maternal age, and emotional states.

  • Paternal factors like exposure to toxins leading to sperm abnormalities can also affect pregnancy outcomes.

Prenatal Care
1. General Information

  • Prenatal care involves screenings and education; it may include social and nutritional support.

  • Exercise during pregnancy is beneficial for regulating blood pressure, controlling weight gain, and improving mental health.

  • Yoga is noted for reducing stress and enhancing immune function.

  • CenteringPregnancy: A program offering group-based prenatal care focused on empowering expectant mothers, showing positive outcomes for both mother and child.

Normal Prenatal Development

  • Prospective parents should manage factors that could harm fetal development, though most development is typically positive.

Birth

Topics

  • The birth process.

  • Assessing the newborn.

  • Preterm and low birth weight infants.

The Birth Process
Stages of Birth

  1. First Stage:

    • Uterine contractions occur 15-20 minutes apart, lasting for up to 1 minute.

    • This longest stage lasts approximately 6-12 hours.

  2. Second Stage:

    • The baby’s head moves through the cervix and birth canal.

    • This lasts about 45 minutes to 1 hour and concludes with the baby’s full emergence.

  3. Third Stage:

    • Afterbirth: The placenta, umbilical cord, and membranes are detached and expelled, taking only a few minutes.

Childbirth Setting and Attendants

  • In the U.S., 98% of births occur in hospitals, with very few at home or in birthing centers.

  • Midwives provide care primarily in pregnancy and labor, with about 9% of births attended by midwives.

  • A doula offers continuous support for the mother throughout the childbirth experience.

Methods of Childbirth

  1. Pain Management Techniques:

    • Analgesia: Provides pain relief.

    • Anesthesia: Blocks sensations.

    • Oxytocin/Pitocin: Used for inducing labor and managing contractions.

  2. Natural Childbirth: Aims to reduce pain and fear through education and relaxation techniques.

  3. Prepared Childbirth (Lamaze Method): Incorporates a specific breathing technique to manage labor pains along with anatomical education.

  4. Cesarean Delivery: Surgical birth method indicated in specific medical conditions (breech position, fetal distress, etc.).

    • Breech position involves the baby being positioned buttocks-first during birth.

    • Debate exists about the benefits versus risks of cesarean delivery.

Assessing the Newborn
Apgar Scale

  • A method to assess newborn health at one and five minutes after birth based on:

    • Heart rate

    • Respiratory effort

    • Muscle tone

    • Body color

    • Reflex irritability

  • Low Apgar scores can indicate the need for long-term educational support or present developmental risks.

Scoring Summary

Score 0

Score 1

Score 2

Heart rate

Absent

Slow (< 100 bpm)

Fast (100 - 140 bpm)

Respiratory effort

No breathing (>1 min)

Irregular and slow

Good breathing with normal crying

Muscle tone

Limp and flaccid

Weak, some motion

Strong active motion

Body color

Blue and pale

Body pink but extremities blue

Entire body pink

Reflex irritability

No response

Grimace

Coughing, sneezing, and crying

Other Assessment Tools

  • Brazelton Neonatal Behavioral Assessment Scale (NBAS): Assesses neurological development and reflexes in the first month of life.

  • Neonatal Intensive Care Unit Neurobehavioral Scale (NNNS): Evaluates the newborn’s behavior, neurological and stress responses, and regulatory capacities.

Preterm and Low Birth Weight Infants

  1. Definitions:

    • Low Birth Weight Infants: Weigh less than 5 pounds 8 ounces.

    • Very Low Birth Weight: Less than 3 pounds 4 ounces.

    • Extremely Low Birth Weight: Less than 2 pounds 3 ounces.

    • Preterm Infants: Born before 35 weeks gestation.

    • Small for Date Infants: Weigh below normal for their gestational age.

  2. Statistics: In 2020, 10.1% of U.S. births were preterm. Engaging in physical activity during pregnancy decreases the risk of preterm delivery.

  3. Consequences: Preterm and low birth weight infants generally face more health problems and developmental challenges, with severity escalating in correlation to prematurity and birth weight.

  4. Nurturing Low Birth Weight and Preterm Infants:

    • Kangaroo Care: Involves skin-to-skin contact with the baby, offering numerous long-term health benefits, including improved respiratory function and cognitive development from early childhood to adulthood.

    • Massage Therapy: Linked to increased weight gain, decreased stress, and shorter hospital stays.

The Postpartum Period

Topics

  • Physical adjustments.

  • Emotional and psychological adjustments.

  • Bonding.

The Postpartum Period

  • Defined as the time following childbirth until the mother returns to a pre-pregnant state.

Physical Adjustments

  • Fatigue can reduce a new mother's well-being and confidence.

  • Sleep loss contributes to stress, marital issues, and poor decision-making.

  • Hormonal changes occur following the delivery of the placenta, resulting in decreased estrogen and progesterone levels until hormone production resumes in the ovaries.

Emotional and Psychological Adjustments
1. Postpartum Depression

  • Affects daily functioning; peaks 3-5 days post-birth, may last for months but often subsides within two weeks without treatment.

  • Risk Factors:

    • Previous depression and anxiety.

    • Low self-esteem.

    • Poor marital relationships.

    • Lack of social support.

    • History of depression.

  • Impact of depression may also affect the infant, particularly if both parents are experiencing depression.

Bonding

  • Bonding: Establishes a physical connection between parents and newborn shortly after birth.

  • Rooming-In: Involves keeping the baby in the mother’s room during their hospital stay to enhance attachment and bonding.

Additional Insights

  • The postpartum experience is often referred to as the "fourth trimester," highlighting the importance and continuity of support for the mother and infant in the initial months following birth.