Prenatal Development

First Trimester: The Foundation (Weeks 1-12)

This is the most sensitive period for the baby, as all major organ systems begin to form.

The Great Beginning (Week 4)*

“Embryo” size of poppy seed, neural tube (becomes brain and spinal cord) begins to close

Organogenesis Peak (Week 8)*

Heart beating 150 times per minute, fingers and toes form, tail disappears, officially a fetus

Second Trimester: The Growth Spurt (Weeks 13-27)

“Honeymoon Phase”, when baby focuses on getting bigger and functional

The Halfway Mark (Week 20)

baby covered in lanugo (fine hair) and vernix (a waxy coating) protects skin from amniotic fluid, digestive system producing meconium (first poop)

The Viability Milestone (Week 24)*

Baby considered “viable” meaning theres a chance of survival if born early, lungs produce surfactant allowing air sacs to form

The Third Trimester: The Finishing Touches (Weeks 28-40)

Focus shifts to brain power, for storage, and lung maturity.

The Brain & Bone Build (Week 32)

Brain develops rapidly, baby practices breathing by inhaling amniotic fluid, bones fully formed but soft and flexible

Early Term (Week 37)

Baby nearly ready, lungs and brain mature, gaining half a pound per week to stay warm

Neural Tube Closure*

Week 4, prevents spinal defects (why folic acid important)

Heartbeat Detection

Weeks 6-7, primary indicator of pregnancy viability

Hearing Develops

Week 18, baby can hear your voice & heartbeat

Eyes Open

Week 27, fetus begins to sense light and dark

Full term

Week 39, optimal time for brain & lung development before birth