Third Trimester & Viability Threshold
Educational content only — not medical advice.
Embryonic Age: 26 weeks post-fertilization — Entry into the third trimester. Eyes open with functioning eyelashes; pulmonary surfactant synthesis ramps up, significantly elevating premature survival rates.
Biometric Measurements
- Approximate Length: 37.6 سم (CRL/CHL - INTERGROWTH-21st)
- Estimated Weight: 1000 جم (1 كجم) (Hadlock)
- Fundal Height: 28 cm
- Size Comparison: Eggplant / Large Butternut Squash
Key Fetal Milestones
- Eyelids unseal; pupillary light reflex emerges
- Type II pneumocytes accelerate pulmonary surfactant production
- Establishment of consolidated sleep-wake cycles and REM brain waves
Maternal Changes
Fundal height measures roughly 28 cm; the ascending uterus begins upward diaphragmatic pressure, often causing mild exertional breathlessness.