First trimester guide: weeks 1 to 13
In the first trimester your baby's organs form, so this is when folic acid and avoiding harmful substances matter most. Expect tiredness, nausea and tender breasts. Book your first appointment as soon as you know you're pregnant, ideally before 10 weeks, and have a dating scan between 8 and 14 weeks.
Key facts
| Folic acid | 400 micrograms daily until 12 weeks (higher dose if advised) |
|---|---|
| Vitamin D | 10 micrograms (400 IU) daily, recommended in the UK |
| First appointment | Ideally before 10 weeks |
| Dating scan | 8 to 14 weeks |
| Caffeine | Under 200 mg a day |
What's happening to your baby
By 13 weeks your baby has gone from a ball of cells to a fetus about the size of a lemon, with a beating heart, arms, legs, fingers and toes. The neural tube, which becomes the brain and spinal cord, closes in the first month, often before you know you're pregnant. See each week in detail in the week-by-week guide.
Common symptoms
- Nausea and vomiting: eat small meals often, keep crackers by the bed, sip fluids between meals rather than with them, and rest.
- Tiredness: often the strongest symptom. Go to bed earlier and accept help.
- Tender breasts, needing to pee more, stronger sense of smell.
- Mood changes: hormones are surging. Tell someone if you feel low most days.
Get help the same day if you can't keep any fluids down for 24 hours. This may be hyperemesis gravidarum, which needs treatment.
Supplements
- Folic acid 400 micrograms a day until 12 weeks. You need a higher dose (usually 5 mg, prescribed) if you have diabetes, a BMI of 30 or more, take epilepsy medicine, or had a previous pregnancy affected by a neural tube defect.
- Vitamin D 10 micrograms a day is recommended in the UK. Many women in the Gulf and South Asia are low in vitamin D despite the sun, so ask for a test.
- Iron only if your blood test shows you need it.
- Avoid supplements with vitamin A (retinol).
Your first appointments
Your first visit usually includes your medical history, blood pressure, weight, urine and blood tests for blood group, anaemia, infections and thalassaemia (common in South Asian and Middle Eastern families). Between 11 and 14 weeks you'll usually be offered combined screening for Down's syndrome and other conditions. Check what's due on the scans and tests timeline.
Food and lifestyle
Avoid alcohol and smoking, keep caffeine under 200 mg a day, and avoid foods with infection risk. Our "Can I eat this?" checker covers local foods like kaleji, papaya, paneer and kingfish.
When to get help
Read morning sickness remedies and early signs of pregnancy. Call your doctor or maternity unit for bleeding, one-sided tummy pain, shoulder-tip pain, fainting, fever, or burning when you pee. Read the full list of warning signs.
Frequently asked questions
When should I tell people I'm pregnant?
Is it safe to exercise?
Can I travel by plane?
Sources
- NHS: Vitamins, supplements and nutrition in pregnancy
- NICE NG201 Antenatal care
- RCOG: Nausea and vomiting in pregnancy (Green-top 69)
General information, not medical advice. Medical disclaimer · How we review content
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