Baby development at week 18
Myelin begins coating nerves. Ears stand out more. Many anatomy ultrasounds happen around weeks 18–22 depending on local practice.
Average size estimates for week 18 are about 14.2 cm and 190 g — roughly pear. Your ultrasound report and clinician’s dating override any website average.
What you might feel
Backaches and hip looseness can start. Sleep positions may need pillows and experimentation.
You are in the second 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
- Scan dates and follow-up notes after ultrasound visits
A calm next step in Preglo
Save scan dates as appointments in Preglo and write questions beforehand.
Also useful: due date calculator · all weeks · Preglo features
Nearby weeks: Week 16 · Week 17 · Week 19 · Week 20
Educational averages only — not medical advice. Contact your clinician for symptoms that worry you, bleeding, severe pain, or reduced movements.