Prenatal Development

Germinal

(Conception – week 2) Zygote divides rapidly and implants in the uterine wall.

Embryonic

(Weeks 3 – 8) Neural tube, heart, and major organs form. Most vulnerable period for birth defects.

Fetal

(Week 9 – birth) Organs mature, body grows rapidly, and the fetus begins to move, hear,

and respond.

Teratogens

any agent, substance, or environmental condition that can disrupt normal fetal development and cause congenital birth defects, intellectual disabilities, growth restrictions, or miscarriage

Alcohol

Fetal alcohol spectrum disorders: facial differences, learning and attention problems.

Nicotine/Vaping

Low birth weight, preterm birth, and higher risk of sudden infant death.

Opiods

Neonatal opioid withdrawal syndrome; tremors, feeding and sleep problems.

Infections

Rubella, Zika, and syphilis can cause hearing loss, brain and organ damage.

Chronic Stress

High maternal cortisol is linked to preterm birth and low birth weight.

Environmental Toxins

Lead and mercury exposure can impair brain development.

Rooting

Turns toward a touch on the cheek

Sucking

Sucks when the mouth is touched

Grasping

Grips an object placed in the palm

Moro

Flings arms out when startled

Babinski

Fans toes when the sole is stroked

Stepping

Makes walking motions when held upright

Vision at birth

Blurry at first; prefers faces and high contrast. Slowest sense to mature.

Hearing at birth

Tuned to human voices; recognizes the parent's voice heard in the womb.

Smell and taste at birth

Prefers sweet tastes and the smell of the parent's milk.

Synaptogenesis

Connections between neurons multiply rapidly in the first years.

Pruning

Connections that are used get stronger; unused ones are removed.

Myelination

Nerve fibers are coated, speeding signals; continues into the mid-20s.

Sensitive periods

early experience matters most for vision, language, and attachment

Brain size in infancy

Brain is roughly 80% of adult brain size by age 3