Prenatal Development Notes

Germinal Stage (0-2 weeks)
Begins with fertilization, where the sperm and egg unite to form a zygote.
The zygote undergoes rapid cell division as it travels down the fallopian tube toward the uterus.
Upon reaching the uterus, it implants into the uterine wall, marking the beginning of the embryo's development and the formation of the germ disc, which will develop into the embryo.
Embryonic Stage (3-8 weeks)
Major organ systems begin to form. The ectoderm will develop into the nervous system, skin, and hair; the mesoderm will become muscles, bones, and the circulatory system; and the endoderm will form internal organs including the digestive system and lungs.
The placenta develops to provide oxygen and nutrients through the umbilical cord and to remove waste products.
By the end of this stage, the embryo has recognizable human features, including developing limbs and facial traits.
Fetal Stage (9 weeks-birth)
Characterized by significant growth and maturation of all organ systems. The fetus gains weight and stores fat.
Home to critical neurological development, especially with the expansion of the cerebral cortex, which supports higher-level brain functions.
The age of viability, when the fetus can survive outside the womb, occurs between 22-28 weeks, and the fetus begins to show responses to sounds and stimuli, laying the groundwork for sensory processing.

Each gamete (sperm/egg) comprises 23 chromosomes, totaling 46 chromosomes in a standard human body cell.
Among these, 22 pairs are autosomes, which are identical in both sexes, while the 23rd pair consists of sex chromosomes (XX for females and XY for males), determining the biological sex of the offspring.
Genes: Specific segments of DNA that encode for proteins influencing various traits; each gene can have multiple forms, or alleles.
Genotype: The complete genetic makeup of an individual, encompassing all inherited traits.
Phenotype: The observable characteristics, such as physical appearance or behaviors, which result from the interaction of the genotype with environmental influences and experiences throughout development.

Mother's Age: Fertility is generally highest in younger women; risks associated with maternal age increase notably after age 35, leading to complications like chromosomal abnormalities (e.g., Down syndrome) and preterm birth.
Nutrition: Adequate nutrition is crucial for healthy fetal development. Insufficient intake of essential nutrients, particularly folic acid, is linked to neural tube defects such as spina bifida. Maternal malnutrition can lead to low birth weight, which elevates risks for infant mortality and long-term developmental issues.
Stress: Chronic stress can negatively impact fetal development, potentially leading to conditions like low birth weight, premature birth, and emotional or behavioral problems. Stress may also trigger poor lifestyle habits, including smoking, substance abuse, and neglecting prenatal care.

Teratogens are harmful agents that can adversely affect fetal development, with several categories:
Drugs: Substances such as alcohol can lead to Fetal Alcohol Spectrum Disorders, while caffeine and nicotine are also linked to adverse birth outcomes.
Diseases: Maternal infections, such as rubella or syphilis, can cause significant developmental issues in the fetus, while diseases like AIDS can be transmitted from mother to child.
Environmental Hazards: Exposure to environmental toxins like lead, mercury, or pesticides can result in developmental disorders and long-term health implications. The effects of teratogens depend on timing (sensitive periods), dosage, and genetic susceptibility of the fetus.

Investigating strategies to foster resilience against teratogens is essential, like public health initiatives aimed at educating mothers and ensuring access to prenatal care.
Reflection on developmental theories, such as the interaction between biological and environmental factors, further deepens the understanding of prenatal influences on lifelong development.