Snapshot: Weeks 1–12 lay the groundwork for every major organ system. Focus on prenatal vitamins, timely check-ups, and evidence-based genetic screening.
What is the First Trimester?
The first trimester covers the first 12 weeks of pregnancy, starting from the first day of your last menstrual period (LMP). Although conception typically happens around week 2 or 3, the LMP is used to calculate gestational age. During this time, your body adjusts to support the pregnancy, and your baby develops from a tiny group of cells into an embryo with the beginnings of vital organs.
🧬 Key Milestones
| Week | Key Development |
|---|---|
| 4–5 | Heart tube begins rhythmic beats |
| 6–7 | Brain & spinal cord start forming |
| 8–9 | Facial features and limb buds appear |
| 10–12 | Organs refine, fingers & toes separate; first tiny movements |
Timeline of embryo growth from Week 4 heartbeat to Week 12 limb movement
🤰 Common First-Trimester Symptoms
- Morning sickness: Nausea and vomiting, often triggered by smells or certain foods, can happen at any time. This is driven by rising levels of human chorionic gonadotropin (hCG).
- Fatigue: Increased progesterone can leave you feeling exhausted as your body works to support the pregnancy.
- Breast tenderness: Hormonal changes may cause sore or swollen breasts as they prepare for milk production.
- Frequent urination: A growing uterus and increased blood flow put pressure on your bladder, leading to more bathroom visits.
- Food cravings or aversions: Hormones can change your sense of taste and smell, causing cravings or dislikes for certain foods.
Tip → Small, frequent meals plus ginger or B6 supplements (if approved) often ease nausea.
🩺 Essential Tests & Check-Ups
| Timing | What Happens | Why It Matters |
|---|---|---|
| Week 8–10 | First prenatal visit: confirm pregnancy, set due date, baseline labs | Establish care & detect early concerns |
| Week 6–9 | Transvaginal ultrasound | Verify heartbeat & gestational age |
| Week 10+ | Non-invasive prenatal testing (NIPT) | Screens for common chromosomal conditions |
| Week 11–13 | Nuchal translucency ultrasound ± serum screen | Assesses chromosomal & structural risks |
🥗 First-Trimester Nutrition
| Nutrient | Daily Target | Food Ideas |
|---|---|---|
| Folic acid | 400–800 µg | Fortified cereals, leafy greens |
| Iron | 27 mg | Lean red meat, lentils |
| Vitamin C | 85 mg | Citrus, berries |
| Hydration | ≥ 2 L water | Flavour with lemon or mint |
Avoid unpasteurised dairy, raw fish, under-cooked meat, and limit caffeine to ≤ 200 mg per day.
🛑 What to Skip
- Alcohol & nicotine
- Hot tubs or saunas (> 38 °C)
- Herbal or OTC meds not cleared by your provider
- Contact sports & activities with fall or dive risk
✅ First-Trimester Checklist
- Book your first prenatal appointment
- Begin a prenatal vitamin with folic acid
- Track daily symptoms in an app or journal
- Explore genetic testing option
- Schedule brief walks or prenatal yoga
Frequently Asked Questions
When will my bump show?
Most first-time parents “show” between Weeks 12–16; earlier in subsequent pregnancies.
Is light spotting normal?
Light, brief spotting can accompany implantation, but heavy bleeding or severe cramps needs urgent medical attention.
Can I travel?
Generally safe if your pregnancy is low-risk. Wear compression socks on flights and carry your prenatal records.
Next Steps
- ➡️ Preview: Second Trimester Guide
- 🧮 Due date calculator
Educational content only — not a substitute for professional medical advice. Always consult your healthcare provider for personalised guidance.
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