18 Weeks Pregnant
Reviewed by Safi Allah Khan
Medically reviewed by: Safi Allah Khan · Written by the Momi team · Last updated 20 October 2026
Quick answer: At 18 weeks pregnant, your baby is about the size of a bell pepper, about 14.2 cm (5.6 in) long. You're in the second trimester, in month 5, with 22 weeks to go until your due date. This week's milestone: hearing developing. Symptoms vary from person to person.
| Week 18 at a glance | |
|---|---|
| Trimester | Second |
| Month | 5 |
| Weeks to due date | 22 |
| Baby's size | About the size of a bell pepper |
| Length | About 14.2 cm (5.6 in) |
| Weight | About 190 g (6.7 oz) |
| This week | Hearing developing |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 18 weeks
Your baby is about the size of a bell pepper and weighs about 190 g (6.7 oz). ACOG notes that around week 18 the fetus can hear sounds. Your voice may become familiar over the coming weeks.
Your body at 18 weeks pregnant
You may feel more hungry, and back aches are common as your posture changes. Some people feel dizzy if they stand up quickly.
Things to do this week
- Attend your anatomy scan if it's this week.
- Wear comfortable, supportive shoes.
- Talk or sing to your baby if you like. It's a nice habit for partners too.
When to call your doctor or midwife
Contact your care team straight away if:
- you have bleeding or fluid leaking from your vagina
- you have severe belly pain that doesn't go away
- you have a fever of 100.4°F (38°C) or higher
- you have a headache that won't go away or gets worse
- you have regular, painful tightenings
If something feels wrong, trust that feeling and call. In an emergency, call your local emergency number.
Track week 18 in Momi
Partners can write their own entries in the Dad's diary section of Momi. Momi follows your pregnancy week by week with your baby's size and development, and keeps your diary, bump photos, appointments, kick counts and contractions in one place.
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Keep reading
← 17 weeks pregnant · All weeks · 19 weeks pregnant →
Sources
- ACOG: Changes During Pregnancy (infographic)
- NHS: Your baby's movements
- NHS: Antenatal care and appointments
- CDC: Urgent Maternal Warning Signs
Medical disclaimer: Momi and this website provide general information, not medical advice. Always talk to your doctor or midwife; in an emergency call your local emergency number.
FAQ
How big is a baby at 18 weeks pregnant?
On average, a baby at 18 weeks is about the size of a bell pepper: about 14.2 cm (5.6 in), about 190 g (6.7 oz). These are typical averages, and healthy babies vary.
How many months is 18 weeks pregnant?
18 weeks pregnant is in the fifth month of pregnancy and the second trimester. Months don't divide evenly into 40 weeks, so different sources may label the month slightly differently.
What should I do at 18 weeks pregnant?
Attend your anatomy scan if it's this week. Wear comfortable, supportive shoes.
Related guides
Track this in Momi
Momi is a free pregnancy tracker app for iPhone and Android that follows pregnancy week by week, estimates the due date, and keeps a pregnancy journal, weight log, kick counter and contraction timer in one place.
