12 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 12 weeks pregnant, your baby is about the size of a lime, about 5.4 cm (2.1 in) long. You're in the first trimester, in month 3, with 28 weeks to go until your due date. This week's milestone: dating scan window. Symptoms vary from person to person.
| Week 12 at a glance | |
|---|---|
| Trimester | First |
| Month | 3 |
| Weeks to due date | 28 |
| Baby's size | About the size of a lime |
| Length | About 5.4 cm (2.1 in) |
| Weight | About 14 g (0.5 oz) |
| This week | Dating scan window |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 12 weeks
Your baby is about the size of a lime and weighs about 14 g (0.5 oz). ACOG says the fetus is about 2 inches long by the end of week 12. The kidneys are making urine.
Your body at 12 weeks pregnant
Your uterus is starting to rise above your pelvic bone. For many, nausea begins to ease over the coming weeks.
Things to do this week
- Have your dating scan if you haven't yet. It gives the most accurate due date.
- Update your due date if the scan changes it.
- Ask about the next appointments in your schedule.
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 12 in Momi
If your scan moved your due date, update it in Momi so your weeks stay correct. 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
← 11 weeks pregnant · All weeks · 13 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 12 weeks pregnant?
On average, a baby at 12 weeks is about the size of a lime: about 5.4 cm (2.1 in), about 14 g (0.5 oz). These are typical averages, and healthy babies vary.
How many months is 12 weeks pregnant?
12 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 12 weeks pregnant?
Have your dating scan if you haven't yet. It gives the most accurate due date. Update your due date if the scan changes it.
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.
