Pre-conception period (weeks 1-2) followed by fertilisation (week 3) and implantation (week 4). The first month covers LMP through the first positive pregnancy test.
PREGNANCY MONTH 1 · WEEKS 1–4 · 1st TRIMESTER
BABY AT START OF MONTH
🔬
microscopic
MONTH
1
of 9 · Weeks 1–4
BABY AT END OF MONTH
🌸
poppy seed
0.1cm · too tiny
WEEK-BY-WEEK DEVELOPMENT — MONTH 1 (WK 1–4)
Week 1: LMP (period) — no conception yet. Gestational calendar starts.
Week 2: Ovulation approaching. Follicle maturing. Fertile window opens.
Week 3: Fertilisation and conception occurs. Zygote divides and travels to uterus.
Week 4: Implantation complete. hCG detectable. Positive pregnancy test possible.
🌸 HOW YOU MAY FEEL
No symptoms in weeks 1-2. Mild spotting (implantation bleeding) possible in week 3. Missed period and breast tenderness appear in week 4.
COMMON SYMPTOMS — MONTH 1
APPOINTMENTS & TESTS — MONTH 1
Week 4-6: Contact GP / OB to confirm pregnancy
Schedule first antenatal appointment
💡 MONTH 1 TIP
Start taking folic acid 400mcg daily if not already — critical for neural tube development in weeks 3-6.
What happens in month 1?
Month 1 (weeks 1-4) covers the earliest stages: Week 1-2: Your period and the lead-up to ovulation. No embryo yet. Week 3: Fertilisation occurs. Zygote divides and travels to uterus. Week 4: Implantation complete. hCG detectable. Positive pregnancy test possible. Baby size at end of month 1: poppy seed (~0.1cm) First symptoms: missed period, breast tenderness, fatigue, mild nausea.
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Pregnancy month 1 · Weeks 1–4 · 1st trimester · Sources: ACOG, NHS, WHO