13 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 13 weeks pregnant, your baby is about the size of a lemon, about 7.4 cm (2.9 in) long. You're in the first trimester, in month 3, with 27 weeks to go until your due date. This week's milestone: last week of trimester one. Symptoms vary from person to person.
| Week 13 at a glance | |
|---|---|
| Trimester | First |
| Month | 3 |
| Weeks to due date | 27 |
| Baby's size | About the size of a lemon |
| Length | About 7.4 cm (2.9 in) |
| Weight | About 23 g (0.8 oz) |
| This week | Last week of trimester one |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 13 weeks
Your baby is about the size of a lemon. All major organs have formed and will keep developing. Bones, especially the long bones, are starting to harden.
Your body at 13 weeks pregnant
This is the last week of the first trimester. Many people notice their energy returning and nausea settling, though this varies.
Things to do this week
- Look back at the first trimester and note anything to raise at your next visit.
- Start planning time off for later appointments.
- Keep taking prenatal vitamins as advised.
When to call your doctor or midwife
Contact your care team straight away if:
- you have vaginal bleeding, especially with cramps or belly pain
- you have severe or one-sided belly pain, or pain in the tip of your shoulder
- you are vomiting so often you can't keep fluids down (the CDC flags being unable to drink for more than 8 hours)
- you have a fever of 100.4°F (38°C) or higher
- it hurts or burns when you pee
If something feels wrong, trust that feeling and call. In an emergency, call your local emergency number.
Track week 13 in Momi
Write a short end-of-trimester entry in your Momi diary. It's a nice one to read back later. 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.
Download Momi free on the App Store or Google Play. Free with ads; optional Premium.
Keep reading
← 12 weeks pregnant · All weeks · 14 weeks pregnant →
Sources
- ACOG: Changes During Pregnancy (infographic)
- NHS: Signs and symptoms of pregnancy
- 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 13 weeks pregnant?
On average, a baby at 13 weeks is about the size of a lemon: about 7.4 cm (2.9 in), about 23 g (0.8 oz). These are typical averages, and healthy babies vary.
How many months is 13 weeks pregnant?
13 weeks pregnant is in the third month of pregnancy and the first trimester. Months don't divide evenly into 40 weeks, so different sources may label the month slightly differently.
What should I do at 13 weeks pregnant?
Look back at the first trimester and note anything to raise at your next visit. Start planning time off for later appointments.
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.
