Fetal Development

The Miracle of Life

A Prenatal Development Timeline

Follow the beautiful journey of a new life from the very first moments of fertilization all the way through to birth.

First Month

Weeks 1 – 4
  • Fertilization takes place, and a new life begins.
  • Cell division occurs, and cells begin to specialize into different tissues.
  • The new life implants securely in the lining of the womb.
  • The heart begins to beat (about 21 days).
  • The foundation of the brain and nervous system is established.
  • Muscle tissue begins forming; arms and legs start to take shape; eye and ear formation is in the early stages.
  • The new life is about the size of an apple seed—not yet ¼ of an inch.

Second Month

Weeks 5 – 8
  • Hands and feet start to beautifully develop.
  • Brain waves can be recorded (around 6 weeks).
  • Eyes begin to darken and simple movements begin.
  • Movements become much more purposeful.
  • Eyelids begin to seal over for protection.
  • The stomach, digestive organs, and permanent kidneys are developing.

Third Month

Weeks 9 – 12
  • All major organ systems have been established.
  • Facial features are becoming more well-formed and distinct.
  • Early fingerprints, fingernails, and toenails have formed.
  • Breathing movements can be detected.
  • The cerebral cortex of the brain has started to form.
  • The child can open and close its mouth, swallow, make a fist, touch its face, and turn its head.
  • The sex of the new life can be visually determined.
  • Approaching four inches in length.

Fourth, Fifth, and Sixth Months

Weeks 13 – 24
  • A period of rapid growth takes place and bones begin the solidifying process.
  • Arm and leg movements become much more coordinated.
  • The unborn child can detect sound.
  • "Quickening" takes place—the mother can feel movement (around 18 weeks).
  • Hair, eyebrows, eyelashes, and all parts of the eye have developed.
  • Rapid eye movements have been detected.
  • The child is about nine inches in length.

Seventh Month Through Birth

Week 25 – Delivery
  • Hearing becomes even more well-developed.
  • Eyelids open.
  • The lungs become more mature and breathing is more rhythmic.
  • Skin becomes smoother as a layer of fat for insulation increases in the last three weeks of pregnancy.
  • The baby weighs about six to nine pounds and is ready for life outside the womb!

Sources: Keith Moore, The Developing Human, 2020. MedlinePlus: National Institutes of Health / U.S. National Library of Medicine.

Note: Times given refer to development after conception. As with all individuals, some variation may exist in time of development. Lengths are measured from the top of the head to the lower trunk.