First trimester
12 weeks pregnant
Your baby is about the size of a plum
- First trimester1st trimester weeks 1–12
- Second trimester2nd trimester weeks 13–26
- Third trimester3rd trimester weeks 27–40+
By Clever Mum Parenting · Parenting guides
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What should you ask at the dating scan?
Check the appointment letter for preparation instructions and write down your questions beforehand. Useful topics include your estimated due date, what the scan can assess and which screening choices are being offered. A dating scan is not a guarantee that every condition can be detected.
The NHS week-12 guide describes a baby roughly 5.4cm from head to bottom. This is an approximate description, not a target measurement for judging your own scan. Symptoms may be easing, persisting or changing; compare concerns with your maternity team rather than another person’s timeline.
After the appointment, keep any dates and contact details together. Decide who you want to tell about the pregnancy in your own time. If an explanation is unclear, ask the team to go through it again before making a screening decision.
Evidence and scope
Published sources consulted on 9 September 2026. NHS: week 12.
How big is the baby at 12 weeks pregnant?
At 12 weeks pregnant, your baby is about the size of a plum, roughly 5.4cm and around 14g. Reflexes are developing — the baby will move if your bump is prodded, though you won't feel it. The digestive system is starting to practise contractions, and the kidneys produce urine. These are typical averages — your midwife's measurements are the ones that matter for your pregnancy.
What might you feel at 12 weeks?
Most people at 12 weeks notice some mix of the symptoms below — and plenty notice none of them. You are nearing the end of the first trimester. Symptoms may begin easing, although this varies and tiredness or nausea can continue. None of this is a diagnosis; contact your midwife if something worries you.
Common symptoms this week
- Energy beginning to return
- Nausea easing
- A hint of a bump for some
Symptom lists are typical, never exhaustive — and having none of them is normal too.
What should you do at 12 weeks pregnant?
The useful job this week is practical, not medical. Many people choose to share their news after the 12-week scan — but there's no right time. Do what feels right for you. Pair it with the NHS week-by-week guide if you want a second description of the same stage.
Week 12 checklist
- Attend your dating scan — your due date is set from the baby's measurements
- Decide who to tell and when — after the scan is common but there's no rule
- Photograph your scan picture rather than laminating it (heat fades them)
What antenatal care is due around 12 weeks?
These appointments, vaccines and deadlines fall around this stage. Your maternity team will confirm your own dates.
- Dating scan (around 10 to 14 weeks). The NHS dating scan confirms how many weeks pregnant you are and your due date, checks for twins and that the pregnancy is in the right place. It usually takes about 20 minutes. What happens at the 12-week scan
- Combined screening, if you choose it. Screening for Down's, Edwards' and Patau's syndromes can be done at the dating scan between 10 and 14 weeks, using a blood test and a nuchal translucency measurement. It is your choice. How screening results work
What else is useful at 12 weeks?
Use the week page for size and symptoms; use the guides below for the decisions that actually sit in this window — pay, packing, car seats, labour signs.
12 weeks pregnant: common questions
Is the 12-week scan the one that dates the pregnancy?
Yes — the dating scan (11–14 weeks) measures the baby crown to rump and sets your official due date, which usually replaces the date calculated from your last period. It also checks the heartbeat, detects twins and includes optional combined screening.
How big is my baby at 12 weeks pregnant?
At 12 weeks, your baby is approximately the size of a plum, about 5.4cm and around 14g. These are approximate averages — every baby grows at its own pace.
What's happening at 12 weeks pregnant?
Reflexes are developing — the baby will move if your bump is prodded, though you won't feel it. The digestive system is starting to practise contractions, and the kidneys produce urine. For you: you are nearing the end of the first trimester. symptoms may begin easing, although this varies and tiredness or nausea can continue.
What appointments or vaccines are due at 12 weeks pregnant?
Around 12 weeks: dating scan; combined screening, if you choose it. Your maternity team will confirm the dates that apply to you.
Which trimester is 12 weeks?
12 weeks pregnant is in the first trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night.