Fetal Development

Fetal development progresses through three trimesters, each marked by distinct changes: the first trimester establishes vital organs and structures, the second focuses on growth and movement, and the third prepares the fetus for birth with weight gain and organ maturation.

🍼 First Trimester (Weeks 1–12)

• Weeks 1–4: Fertilization occurs, and the embryo implants in the uterine wall. Basic structures like the neural tube (future brain and spinal cord) begin forming.
• Weeks 5–8: Heart starts beating, limb buds appear, and facial features begin to develop. Major organs (liver, kidneys) start forming.
• Weeks 9–12: The embryo becomes a fetus. External genitalia start differentiating, fingernails and toenails form, and the fetus begins small movements (though not yet felt by the mother).

👶 Second Trimester (Weeks 13–26)

• Weeks 13–16: The fetus grows rapidly, facial expressions appear, and the skeleton begins to harden.
• Weeks 17–20: The mother may feel quickening (first fetal movements). Fine hair (lanugo) and a protective coating (vernix caseosa) cover the skin.
• Weeks 21–24: Lungs begin producing surfactant, essential for breathing after birth. The fetus responds to sounds and light.
• Weeks 25–26: The nervous system matures, and the fetus develops sleep-wake cycles.

👼 Third Trimester (Weeks 27–40)

• Weeks 27–32: Rapid brain development occurs, pupils can respond to light, and bones continue to strengthen.
• Weeks 33–36: The fetus gains weight quickly, fat layers form under the skin, and the immune system strengthens through maternal antibody transfer.
• Weeks 37–40: The fetus is considered full-term. Organs are fully developed, the head often engages in the pelvis, and the baby prepares for birth.