12 weeks pregnant: the first trimester draws to a close
A milestone week for many: the scan, the first photo, maybe telling more people. And for many, the nausea starts to lift.
Updated October 13, 2026 · sources checked October 13, 2026
In short
At 12 weeks you are at the end of month three, close to the end of the first trimester. The NHS says your baby is 5.4 cm from head to bottom, with internal organs, muscles and a skeleton hardening into bone. The one thing to do this week: go to your dating scan if it is booked, then decide when to tell your employer.
Where you are at 12 weeks
Twelve weeks is the end of month three in Cleveland Clinic's grouping. Whether you are still in the first trimester depends on who you ask: ACOG counts it to 13 weeks and 6 days, while the NHS week-by-week guide starts the second trimester at week 13. Either way, the NHS says you are hopefully starting to feel much better. Check your exact week with the pregnancy week calculator, and expect your due date to be confirmed, and sometimes adjusted, at the scan.
Your baby this week
The NHS gives a length of 5.4 cm from head to bottom and compares your baby to a plum. Cleveland Clinic says that at the end of month three the fetus is about 2.5 to 3 inches long.
- Internal organs and muscles have grown, and the skeleton is hardening from tissue into bone (NHS).
- The heartbeat can be picked up on an ultrasound scan.
- The sex organs have formed, though most scans cannot show the sex yet.
- Cleveland Clinic adds that the circulatory, digestive and urinary systems are working and your baby drinks and pees amniotic fluid.
Your body: appetite, weight and your bump
As sickness eases, you may feel hungrier. The placenta has probably taken over feeding your baby, and your hormones calm down a little (NHS).
- No eating for two. The NHS says most people gain 10 kg to 12.5 kg (22 lb to 26 lb), mostly after week 20, and some gain none. Extra calories are only suggested from the third trimester, around 200 a day.
- Your bump depends on hormones, pre-pregnancy weight, previous pregnancies and muscle strength: there is no right size now.
- Folic acid: the NHS advises it until at least week 12. The MRC Vitamin Study (1991) found a 72% protective effect against neural tube defects in high-risk women, which is why this early window matters.
Your symptoms may still include tiredness, nausea, heartburn and an aching stomach.
Is this normal? When to call
Call your maternity unit, early pregnancy unit or NHS 111 (UK), or your OB-GYN or midwife (US), for any bleeding or unusual discharge, tummy pain that does not settle, or a temperature of 38C (100.4F) or above. Call 999 or 911 for heavy bleeding with severe pain, shoulder pain or if you feel faint.
Cleveland Clinic notes that the chance of miscarriage drops considerably after 12 weeks. If you have had a loss before, this week can still feel tense, and that is understandable. Miscarriage UK (0303 003 6464) and Share Pregnancy and Infant Loss Support in the US support people in later pregnancies after a loss too.
The dating scan
In England the dating scan is offered at around 10 to 14 weeks (NHS 12-week scan page). It checks how many weeks pregnant you are and your due date, whether there is more than one baby, that the baby is growing in the right place, and your baby's development; it can also detect some conditions such as spina bifida. If you have chosen screening and the scan is between 10 and 14 weeks, the combined test for Down's, Edwards' and Patau's syndromes is usually done at the same time. If your scan happens after 14 weeks, you will be offered a different blood test between 14 and 20 weeks instead.
In the US, first-trimester screening (blood test and nuchal translucency) is usually done between 10 and 13 weeks, and cell-free DNA from 10 weeks (ACOG).
Telling work, and planning ahead
The NHS notes that many people tell their employer after 12 weeks and the first scan. In the UK, once you tell your employer you have maternity rights, including paid time off for antenatal appointments and a risk assessment of your workplace. The legal latest is 15 weeks before your due date (GOV.UK). In the US, the Pregnant Workers Fairness Act requires reasonable accommodations from employers with 15 or more employees (EEOC).
The NHS also suggests visiting local maternity units to think about where to give birth, and starting to think about contraception after the birth, since a short gap between pregnancies can cause problems.
Your week 12 checklist
For your partner
Come to the scan if you can, and help plan who hears the news and when: this is a shared announcement, at her pace.
Previous and next week
Week 11: the placenta takes over · Week 13: a small bump and healthy gums · The first trimester · All weeks
Questions parents ask
12 weeks pregnant is how many months?
About three months. Cleveland Clinic groups weeks 9 to 12 as the third month and says that if you are three months pregnant, you are about 12 weeks. Weeks are used in pregnancy because months have different lengths.
Should I have a bump at 12 weeks?
Not necessarily. The NHS says that in a first pregnancy you might not start showing until around 12 weeks or later, and that bump size depends on hormones, pre-pregnancy weight, how many babies you have had and muscle strength. A small or invisible bump is normal.
Is week 12 the end of the first trimester?
Sources differ. The NHS week-by-week guide treats week 13 as the start of the second trimester; ACOG defines the first trimester as running to 13 weeks and 6 days.
Can I stop taking folic acid at 12 weeks?
The NHS advises 400 micrograms of folic acid a day until at least week 12, and suggests considering a daily vitamin D supplement from October to early March. Ask your midwife or doctor whether to continue a prenatal vitamin.
Sources
- NHS — Week-by-week guide: week 12 checked October 13, 2026
- NHS — 12-week scan checked October 13, 2026
- Cleveland Clinic — Fetal development: week-by-week stages of pregnancy checked October 13, 2026
- ACOG — How Your Fetus Grows During Pregnancy (trimester definitions) checked October 13, 2026
- GOV.UK — Maternity pay and leave: how to claim checked October 13, 2026
- MRC Vitamin Study Research Group (1991), The Lancet — Prevention of neural tube defects (PMID 1677062) checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.