Baby development at week 5
Week 5 is a foundational week for the brain and spinal cord. A tube-like structure folds, and cardiac cells start organizing into a primitive heart tube.
Average size estimates for week 5 are about 0.2 cm and too early to weigh meaningfully — roughly sesame seed. Your ultrasound report and clinician’s dating override any website average.
What you might feel
Heightened smell, food aversions, or deeper fatigue can show up. Mood swings are common as hormones rise.
You are in the first trimester. Two pregnancies at the same week can feel completely different — treat these notes as orientation, not a checklist you must match.
What to track this week
- Symptoms, mood, sleep, and energy in your daily log
- Water intake toward a simple daily goal
- Appointment dates and questions for your care provider
A calm next step in Preglo
Ask your clinician about prenatal vitamins (especially folate). Use Preglo’s daily log for symptoms you want to remember between appointments.
Also useful: due date calculator · all weeks · Preglo features
Nearby weeks: Week 3 · Week 4 · Week 6 · Week 7
Educational averages only — not medical advice. Contact your clinician for symptoms that worry you, bleeding, severe pain, or reduced movements.