Biological Beginnings: Prenatal Development, Birth, and the Postpartum Period
The Evolutionary Perspective
Selection and Adaptation- Natural selection is the evolutionary process by which those individuals of a species that are best adapted are the ones that survive and reproduce.
Primary tenet: Those who who are better adapted survive more frequently than those who are less adapted.
Charles Darwin is the historical reference for natural selection.
Evolutionary Psychology- Emphasizes the importance of adaptation and reproduction (i.e., survival of the fittest) in shaping human behavior.
Fit: the ability to bear offspring that survive long enough to bear offspring of their own.
Those deemed “fittest” have more opportunities to pass their genes to the next generation.
Evaluating Evolutionary Psychology- Bidirectional view: biological and environmental conditions influence each other.
Evolution gave us bodily structures and biological potentialities, but it does not dictate behavior.
Notable idea: behavior emerges from dynamic interactions between biology and environment (examples discussed by scholars such as Albert Bandura).
Genetic Foundations of Development
Genetic code and inheritance- Each of us carries a genetic code inherited from our parents.
A fertilized human egg carries this code and begins life as a single cell containing all our genetic information.
Weighs 266 ext{ ounces?} not exactly—correctly, the fertilized ovum is tiny; one cell is often cited as ~1/20{,}000{,}000 ext{ ounce} in older sources. For study purposes: a zygote starts as a single cell containing the full genome.
Fertilization- An egg and a sperm fuse to create a single cell, the zygote.
The 23 unpaired chromosomes from the egg and the 23 unpaired from the sperm combine to form one set of 23 paired chromosomes.
Each parent contributes half of the offspring’s genetic material.
Diploid number: 2n = 46 (23 pairs).
Genotype & Phenotype- Genotype: an individual’s genetic material (e.g., susceptibility genes, longevity genes).
Phenotype: observable characteristics (physical traits like height, weight, hair color; psychological traits like personality and intelligence).
Polygenic Inheritance- Most characteristics are polygenically determined (influenced by many genes).
Few traits are the result of a single gene or a single gene pair; complex interactions shape multiple traits.
Interaction of Heredity and Environment- Behavior genetics seeks to discover the influence of heredity and environment on individual differences in traits and development.
Twin studies and adoption studies are common approaches.
Twin / Adoption Studies- Twin studies compare behavioral similarities between identical twins vs. fraternal twins.
Adoption studies examine whether adopted children resemble their adoptive parents or their biological parents.
Prenatal Development and the Three Periods
Course of prenatal development- Human gestation lasts approx. 266 ext{ days} \ (= 38 ext{ weeks}) from fertilization to birth.
From the last menstrual period, gestation is about 40 ext{ weeks}.
Three periods: Germinal, Embryonic, Fetal.
Note: These are not exactly the same as the three traditional trimesters.
The Germinal Period (First two weeks after conception)- Key events:
Fertilization (formation of zygote).
Cleavage (cell division via mitosis).
Implantation of the blastocyst into the uterine wall.
Timeline highlights:
By day 1–2: single cell begins division.
By day 3: 16–32 cells form a compact ball.
By day 4: hollow ball with 64–128 cells (blastocyst).
By day 5: inner cell mass forms; blastocyst still free in uterus.
By day 6–7: blastocyst attaches to the uterine wall.
By days 11–15: blastocyst invades and implants in the uterine wall.
Structure:
Blastocyst: inner cell mass that will develop into the embryo.
Trophoblast: outer layer that provides nutrition and support for the embryo.
Implantation: attachment to the uterine wall (takes about 10–14 ext{ days} after conception).
The Embryonic Period (Two to eight weeks after conception)- Major processes:
Rate of cell differentiation intensifies.
Early development of body parts and organ systems.
Three germ layers and their derivatives:
Endoderm: later develops into digestive and respiratory systems.
Mesoderm: forms the circulatory system, bones, and muscles.
Ectoderm: forms the nervous system and sensory receptors.
Organogenesis: process of organ formation during the first two months; organs are particularly vulnerable to environmental influences.
Life-support systems develop rapidly:
Amnion, umbilical cord, and placenta become functional supports.
Life Support Systems (during prenatal development)- Amnion: a bag containing clear fluid in which the developing embryo floats; provides temperature and humidity control.
Umbilical cord: contains two arteries and one vein; connects baby to placenta.
Placenta: disk-shaped tissue with tiny blood vessels from the mother and fetus that intertwine but do not join; facilitates exchange of nutrients and wastes between mother and fetus.
The Fetal Period (Two months after conception to birth)- Timeframe: lasts ext{from 2 months to around 7 months}; more generally, from approximately the end of the embryonic period to birth.
Growth milestones by month:
3 months: ext{length} \rightarrow 3 ext{ inches}, ext{weight} \rightarrow 1 ext{ ounce}
4 months: ext{length} \rightarrow 6 ext{ inches}, ext{weight} \rightarrow 4 ext{–}7 ext{ ounces}
5 months: ext{length} \rightarrow 12 ext{ inches}, ext{weight} \rightarrow ext{about } 1 ext{ pound}
6 months: ext{length} \rightarrow 14 ext{ inches}, ext{weight} \rightarrow 1.5 ext{–}2 ext{ pounds}
7 months: ext{length} \rightarrow 16 ext{ inches}, ext{weight} \rightarrow 3 ext{ pounds}
Developmental viability: typically around ext{beginning of the third trimester, \approx} 24 ext{ weeks} after conception.
Birth: Average American baby is roughly 20 ext{ inches} long and weighs about 7.5 ext{ pounds}.
The Brain and Neurodevelopment in Utero- Neural tube formation: occurs around 18–24 ext{ days} after conception.
Neural tube defects (NTDs): anencephaly and spina bifida; folic acid reduces risk of NTDs.
Neurogenesis: generation of new neurons can reach up to 2 \times 10^5 ext{ neurons per minute}.
Neuronal migration: occurs roughly between 6–24 ext{ weeks}; cells move to their proper locations to form brain regions.
Synaptic connections: begin forming around the 23^{\text{rd}} ext{ prenatal week}.
Prenatal Tests and Morbidity/Mortality-Related Concepts
Prenatal tests and imaging- Ultrasound (sonography): non-invasive, uses high-frequency sound waves.
Fetal MRI: more detailed imaging when needed.
Chorionic villus sampling (CVS): 11–13 ext{ weeks}; small placental tissue sample; optional.
Amniocentesis: 15–18 ext{ weeks}; sample of amniotic fluid tested for chromosome or metabolic disorders; optional.
Maternal blood screening: 16–18 ext{ weeks}; identifies pregnancies with elevated risk for certain birth defects (e.g., Down syndrome, neural tube defects).
Triple screen: measures three substances in the mother’s blood; if abnormal, follow-up with ultrasound and possibly amniocentesis.
Infertility and reproductive technology- Approximately 10–15 ext{ percent} of couples in the United States experience infertility.
Infertility is defined as the inability to conceive after 12 ext{ months} of regular intercourse without conception.
In vitro fertilization (IVF): egg and sperm are combined in a laboratory dish; when fertilized, the embryo is transferred into the uterus.
Miscarriage and stillbirth- Stillbirth and miscarriage are discussed as part of prenatal outcomes; scholarly discussions exist on experiences and hospital contexts as noted in the slide (e.g., qualitative studies and recent literature).
Hazards to Prenatal Development
Teratogen definition- Any agent that can cause birth defects or negative cognitive/behavioral outcomes.
Examples include: prescription or psychoactive drugs, incompatible blood types, environmental pollutants, infectious diseases.
Parental factors- Maternal factors: diet/nutrition, obesity, folic acid intake, mercury exposure, maternal age, emotional states and stress, anxiety and depression.
Paternal factors: exposure to radiation, lead, pesticides; smoking; quality of partner relationship and support.
The Birth Process and Postpartum Period
The birth process (three stages)- First stage: uterine contractions cause the cervix to stretch and open.
Second stage: delivery begins as the baby’s head moves through the cervix.
Third stage: afterbirth; placenta, umbilical cord, and membranes are expelled.
Birth setting and attendants- In the United States, approximately 98 ext{ percent} of births occur in hospitals.
Midwives: provide care through pregnancy, birth, and postpartum; about 9.1 ext{ percent} of deliveries attended by a midwife.
Doulas: provide continuous physical, emotional, and educational support before, during, and after childbirth.
Methods of childbirth- Vaginal delivery.
Cesarean delivery (C-section): around 31.9 ext{ percent} of US births; may be life-saving but carries risks of major surgery.
Notable complications illustrated: breech position, umbilical cord prolapse (cord comes before the baby or through the cervix).
APGAR scale- Used to assess newborn health at 1 ext{ minute} and 5 ext{ minutes} after birth.
Five signs assessed, each scored 0, 1, ext{ or } 2:
Appearance (skin color)
Pulse (heart rate)
Grimace (reflex irritability)
Activity (muscle tone)
Respiration (breathing)
Total score ranges from 0 ext{ to } 10.
Low birth weight and pre-term infants- Low birth weight (LBW): less than 5 ext{ pounds } 8 ext{ ounces}.
Very low birth weight (VLBW): less than 3 ext{ pounds } 4 ext{ ounces}.
Extremely low birth weight (ELBW): less than 2 ext{ pounds } 3 ext{ ounces}.
Preterm: born 3 ext{ weeks or more} before full term (before the 37^{\text{th}} ext{ week}).
Small-for-date: birth weight is below normal for pregnancy length.
Nurturing LBW and preterm infants- Kangaroo care: skin-to-skin contact for 2–3 ext{ hours per day} for extended periods in early infancy.
Massage therapy: firm stroking with the palms, three times per day for 15 ext{ minutes}.
Bonding: formation of a physical and emotional connection between parents and newborn in the period shortly after birth.
The Postpartum Period
Postpartum period: lasts roughly 6 ext{ weeks} after childbirth, or until the mother’s body has largely returned to pre-pregnant state.- Physical and psychological adjustments occur as the body involutes (e.g., uterus returning to pre-pregnant size).
Involution: the process by which the uterus returns to its pre-pregnant size.
Emotional and psychological adjustments- Postpartum blues: experienced by about 70 ext{ percent} of new mothers; symptoms begin 2–3 ext{ days} after birth and subside within 1–2 ext{ weeks}.
Postpartum depression: about 10 ext{ percent}; a major depressive episode that can linger for weeks or months and interfere with daily functioning.
Other women may experience no symptoms (roughly 20 ext{ percent} in the cited breakdown).
Connections, Applications, and Real-World Relevance
Integrates several foundational concepts from earlier lectures- How genetic foundations interact with prenatal environments to shape development (nature and nurture in action).
The role of evolution in shaping human development and behavior from a biological perspective, balanced by environmental influences.
Practical implications- Prenatal care and screening can reduce risk and support healthy outcomes (e.g., folic acid to reduce neural tube defects).
Understanding teratogens guides behavior and policy decisions for expectant parents.
Postpartum care (mood monitoring, support systems) is critical for maternal and infant well-being.
Formulas and Key Quantities (summary in LaTeX)
Zygote and chromosome basics- Diploid chromosome number: 2n = 46 (23 pairs).
Gamete chromosome count: n = 23 per gamete.
Gestation lengths- From fertilization to birth: 266 ext{ days} \ (~38 ext{ weeks}).
From last menstrual period to birth: 40 ext{ weeks}.
Ideas for Study
Vocabulary Review:
natural selection: The evolutionary process by which those individuals of a species that are best adapted are the ones that survive and reproduce.
evolutionary psychology: Emphasizes the importance of adaptation and reproduction (i.e., survival of the fittest) in shaping human behavior.
genotype: An individual’s genetic material (e.g., susceptibility genes, longevity genes).
phenotype: Observable characteristics (physical traits like height, weight, hair color; psychological traits like personality and intelligence).
zygote: A single cell formed when an egg and a sperm fuse, containing all genetic information.
blastocyst: A hollow ball of cells with 64–128 cells formed by day 4, possessing an inner cell mass that will develop into the embryo, and an outer layer (trophoblast) that provides nutrition.
teratogen: Any agent that can cause birth defects or negative cognitive/behavioral outcomes.
APGAR scale: Used to assess newborn health at 1 minute and 5 minutes after birth, based on five signs: Appearance, Pulse, Grimace, Activity, Respiration.
preterm: Born 3 weeks or more before full term (before the 37^{\text{th}} ext{ week}).
postpartum blues: Experienced by about 70 percent of new mothers, symptoms begin 2–3 days after birth and subside within 1–2 weeks.
postpartum depression: A major depressive episode experienced by about 10 percent of new mothers that can linger for weeks or months and interfere with daily functioning.
involution: The process by which the uterus returns to its pre-pregnant size.
Process and Timeline Recall:
Outline the three periods of prenatal development (Germinal, Embryonic, Fetal), including their durations and major events/milestones.
Germinal Period (First two weeks after conception): Fertilization (zygote formation), cleavage (cell division), implantation of blastocyst into uterine wall.
Embryonic Period (Two to eight weeks after conception): Intense cell differentiation, early development of body parts and organ systems (organogenesis), formation of three germ layers (endoderm, mesoderm, ectoderm), and life-support systems (amnion, umbilical cord, placenta).
Fetal Period (Two months after conception to birth): Significant growth and maturation of organ systems, developmental viability around 24 weeks.
Trace the major steps of neurodevelopment in utero: neural tube formation, neurogenesis, neuronal migration, and synaptic connections.
Neural tube formation: Occurs around 18–24 days after conception, forming the precursor to the brain and spinal cord.
Neurogenesis: Generation of new neurons, reaching up to 2 \times 10^5 ext{ neurons per minute}.
Neuronal migration: Occurs roughly between 6–24 weeks, cells move to their proper locations to form brain regions.
Synaptic connections: Begin forming around the 23^{\text{rd}} ext{ prenatal week}, allowing neurons to communicate.
Detail the three stages of the birth process.
First stage: Uterine contractions cause the cervix to stretch and open (dilation and effacement).
Second stage: Delivery begins as the baby’s head moves through the cervix and birth canal (expulsion).
Third stage: Afterbirth; placenta, umbilical cord, and membranes are expelled.
Distinctions and Comparisons:
Compare and contrast identical vs. fraternal twin studies and adoption studies in behavior genetics.
Twin studies: Compare behavioral similarities between identical (monozygotic, 100% shared genes) twins vs. fraternal (dizygotic, ~50% shared genes) twins, typically raised in similar environments, to estimate genetic influence.
Adoption studies: Examine whether adopted children resemble their adoptive parents (environmental influence) or their biological parents (genetic influence) to disentangle heredity and environment.
Distinguish between the three germ layers (Endoderm, Mesoderm, Ectoderm) and their resulting organ systems.
Endoderm: Develops into the digestive and respiratory systems.
Mesoderm: Forms the circulatory system, bones, and muscles.
Ectoderm: Forms the nervous system and sensory receptors (e.g., skin, hair, nails).
Understand the differences between various prenatal tests (Ultrasound, Fetal MRI, CVS, Amniocentesis, Maternal Blood Screening).
Ultrasound (sonography): Non-invasive, uses high-frequency sound waves to create images of the fetus; used for general health, growth, and structural assessment.
Fetal MRI: More detailed imaging, typically used if ultrasound raises concerns, to examine brain or other organ structures more closely.
Chorionic Villus Sampling (CVS): Performed 11–13 weeks; small placental tissue sample taken to test for chromosome or metabolic disorders; carries a slight risk of miscarriage.
Amniocentesis: Performed 15–18 weeks; sample of amniotic fluid taken to test for chromosome or metabolic disorders; carries a slight risk of miscarriage.
Maternal Blood Screening (Triple/Quad Screen): Performed 16–18 weeks; measures substances in the mother’s blood (e.g., AFP, hCG, estriol) to identify elevated risk for certain birth defects (e.g., Down syndrome, neural tube defects); non-diagnostic.
Compare the characteristics of postpartum blues, postpartum depression, and the percentage of women experiencing no symptoms.
Postpartum blues: Experienced by ~70% of new mothers; symptoms (mood swings, anxiety, sadness, irritability) begin 2–3 days after birth and subside within 1–2 weeks; generally mild and transient.
Postpartum depression: Experienced by ~10% of new mothers; a major depressive episode that can linger for weeks or months, severely interfering with daily functioning, requiring medical intervention.
No symptoms: Roughly 20% of women experience none of these postnatal mood disturbances.
Application and Critical Thinking:
Explain how heredity and environment interact to influence development, providing examples.
Answer: Development is a bidirectional process where genetic predispositions (heredity) are expressed and shaped by environmental factors (nurture). For example, a child may inherit a genetic predisposition for high intelligence (genotype), but their access to quality education, stimulating home environment, and nutritional intake (environment) will significantly influence whether this potential is fully realized (phenotype). Similarly, a genetic susceptibility to a certain disease might only manifest if exposed to specific environmental triggers.
Identify common teratogens and describe their potential impact on prenatal development.
Common Teratogens: Prescription drugs (e.g., some antidepressants, retinoids), psychoactive drugs (e.g., alcohol, nicotine, cocaine), incompatible blood types (e.g., Rh incompatibility), environmental pollutants (e.g., lead, mercury, pesticides), and infectious diseases (e.g., rubella, Zika, syphilis).
Potential Impact: Teratogens can cause birth defects (e.g., limb deformities from Thalidomide, facial anomalies from Fetal Alcohol Syndrome), growth retardation, cognitive impairments (e.g., intellectual disabilities), behavioral problems (e.g., hyperactivity), and even fetal death, depending on the dose, timing of exposure during prenatal development, and genetic susceptibility of the fetus.
Discuss the importance of prenatal care, folic acid, and support systems for maternal and infant well-being.
Prenatal Care: Regular prenatal check-ups allow for early detection and management of potential complications, monitoring fetal growth, and providing education on healthy pregnancy practices. It significantly reduces the risk of adverse outcomes for both mother and baby.
Folic Acid: Crucial for early neural tube development. Adequate intake before and during early pregnancy drastically reduces the risk of neural tube defects (NTDs) like spina bifida and anencephaly.
Support Systems: Emotional, physical, and educational support from partners, family, friends, or healthcare professionals (like doulas or midwives) can alleviate stress, improve maternal mental health, encourage healthy behaviors, and enhance the bonding experience. This positively impacts both maternal well-being and infant development.
Describe the components of the APGAR scale and how it assesses newborn health.
Components (scored 0, 1, or 2):
Appearance (skin color): Blue-gray (0), pink body/blue extremities (1), completely pink (2).
Pulse (heart rate): Absent (0), below 100 bpm (1), above 100 bpm (2).
Grimace (reflex irritability): No response (0), grimace (1), sneeze/cough/pull away (2).
Activity (muscle tone): Limp (0), weak/inactive (1), strong/active (2).
Respiration (breathing): Absent (0), slow/irregular (1), good cry (2).
Assessment: Administered at 1 and 5 minutes after birth. A total score ranging from 0 to 10 is given. Scores of 7-10 are generally considered healthy, 4-6 suggest some problems, and 0-3 indicate severe distress requiring immediate medical attention. It provides a quick overview of the newborn's physiological status and adaptation to extrauterine life.