Prenatal Development and Birth: Study Notes for Psychology Students

Prenatal Development and Birth

Introduction

Prenatal development encompasses the process from conception to birth, involving complex biological and psychological changes. Understanding these stages is essential for psychology students, as early development can have profound effects on later behavior, cognition, and health.

Conception

Fertilization and Gametes

• Conception occurs when a sperm cell penetrates an ovum (egg cell), resulting in fertilization.

• Gametes are reproductive cells (sperm and ovum) that each contain 23 chromosomes.

• At conception, the 23 chromosomes from the sperm unite with the 23 chromosomes from the ovum, forming a fertilized cell called a zygote with 46 chromosomes (23 pairs).

Example: If a sperm carrying an X chromosome fertilizes the ovum, the resulting zygote will be genetically female (XX); if it carries a Y chromosome, the zygote will be male (XY).

Implantation

• Implantation occurs between 5 to 15 days after intercourse, when the zygote embeds itself in the lining of the uterus.

• This marks the beginning of pregnancy.

Pregnancy

Overview of Trimesters

• Pregnancy is divided into three trimesters, each with distinct developmental milestones and maternal changes.

First Trimester (Conception – 12 Weeks)

• Prenatal care is crucial to prevent birth defects, as all major organs form during this period.

• Physical changes: cessation of menstruation, breast enlargement, fatigue, and morning sickness.

• Greatest risk of miscarriage occurs during this trimester.

Second Trimester (13 – 26 Weeks)

• Noticeable weight gain and expansion of the uterus.

• Fetal movements are felt by the pregnant person.

• Regular prenatal visits monitor both maternal and fetal health.

Third Trimester (27 Weeks to Labour)

• Continued weight gain and abdominal enlargement.

• Increased emotional connection to the fetus.

• Enhanced monitoring to prevent complications.

Assisted Human Reproduction

• Fertility drugs and in vitro fertilization (IVF) are used for individuals with conception difficulties.

• Cryopreservation allows embryos to be frozen for future use.

• Artificial insemination involves injecting sperm directly into the uterus.

Prenatal Development

Patterns of Development

• Cephalocaudal pattern: Development proceeds from the head downward.

• Proximodistal pattern: Development proceeds from the center of the body outward.

Stages of Prenatal Development

• Germinal Stage: First two weeks post-conception, from fertilization to implantation.

• Embryonic Stage: Weeks 2 to 8; major organs and structures begin to form.

• Fetal Stage: Week 8 to birth; growth and refinement of organ systems.

Key Structures

• Placenta: Organ that allows nutrient and waste exchange between mother and embryo without mixing blood.

• Umbilical cord: Connects embryo/fetus to the placenta.

• Amnion: Fluid-filled sac (amniotic fluid) that cushions and protects the developing fetus.

Developmental Milestones

• Neurons form the neural tube, which develops into the brain and spinal cord.

• Gonads (sex glands) develop by week 6.

• Organogenesis: Formation of organs, largely complete by week 8.

• Viability: The fetus's ability to survive outside the womb, typically after 24 weeks.

Examples of Fetal Development

• Fingerprints, facial expressions, and reflexes develop.

• Heartbeat detectable, hair follicles form, and fetus responds to sound and light.

• Vernix (protective substance) covers the skin; lungs produce surfactant for breathing.

• Rapid growth and fat deposition occur in the final weeks.

Disruptions in Prenatal Development

Genetic and Chromosomal Disorders

• Congenital anomaly: An abnormality present at birth.

• Autosomal disorders: Caused by genes on non-sex chromosomes.

• Sex-linked disorders: Usually associated with genes on the X chromosome.

• Trisomy: Condition where there are three copies of a specific chromosome (e.g., Down syndrome is trisomy 21).

Teratogens

• Teratogens are agents (e.g., drugs, infections, chemicals) that can cause harm to the embryo or fetus.

• The greatest risk from teratogens is during the first eight weeks, when organ systems are developing most rapidly.

• Examples include maternal diseases, prescription and psychotropic drugs, tobacco, and alcohol.

• Exposure can lead to miscarriage, stillbirth, premature birth, low birth weight, and neurobehavioral disorders.

Birth and the Neonate

The Physical Process of Birth

• Birth involves dilation of the cervix, delivery of the baby, and expulsion of the placenta (afterbirth).

• Delivery may occur vaginally or via Caesarean section if complications arise (e.g., fetal distress, stalled labor, or maternal health issues).

• Postpartum recovery typically takes about six weeks, with medical follow-up recommended.

Assessing the Neonate

• Neonate: Term for a newborn from birth to one month old.

• The Apgar Scale is used to assess the health of newborns immediately after birth.

• Standard screening for metabolic disorders is also performed.

The Apgar Scale

The Apgar Scale evaluates five criteria: heart rate, respiratory effort, muscle tone, reflex response, and color. Each is scored from 0 to 2, with a maximum total score of 10.

Criterion	Score 0	Score 1	Score 2
Heart Rate	Absent	< 100 beats/minute	> 100 beats/minute
Respiratory Effort	No breathing	Weak cry, shallow breathing	Good cry, regular breathing
Muscle Tone	Flaccid	Some flexion of extremities	Well-flexed extremities
Reflex Response	None	Grimace	Crying, active response
Color	Body pale/blue	Body pink, extremities blue	Completely pink

Summary Table: Stages of Prenatal Development

Stage	Time Frame	Main Events
Germinal	0-2 weeks	Fertilization, cell division, implantation
Embryonic	2-8 weeks	Organogenesis, neural tube formation, placenta develops
Fetal	8 weeks-birth	Growth, organ refinement, viability, sensory development

Additional info: Early prenatal care, avoidance of teratogens, and regular monitoring are critical for healthy development and birth outcomes.