Conception Calculator — Week 4 From Conception (Fetal Age)
You are 4 weeks from conception, which corresponds to 6 weeks of gestational age (LMP-based). This page focuses on true fetal age — how long the baby has actually been developing since fertilisation.
Conception Calculator
Enter your LMP. Fetal age = gestational age − 2 weeks.
How to Use This Calculator
1. Enter the LMP date
Use the labelled fields and units that match your situation.
2. Calculate instantly
The result, visual comparison, and working update as values change.
3. Discuss the estimate with your clinician
Check assumptions, then copy, print, or share the calculation.
Practical Examples & Use Cases
| Starting date | Method | Calculation | Planning use |
|---|---|---|---|
| 1 Jan | LMP | +280 days | Estimated due date |
| Known clinical date | Ultrasound | Clinician dating | Confirm or revise estimate |
Baby at week 4
At 4 weeks from conception (6w gestational): Implantation occurs day 6–10 after fertilisation. The blastocyst splits into embryo + placenta. hCG production begins.
Mother's body — what changes
4 weeks post-conception, your body is: Implantation spotting possible (light pink/brown, 1–2 days). Home pregnancy test may turn positive at the end of the week.
Nutrition & supplements
Focus on folic acid 400–600 mcg/day (neural tube), iodine 150 mcg, and small frequent meals to counter nausea. No extra calories yet — normal maintenance intake is adequate. Week 4 from conception (6 weeks gestational) needs targeted micronutrients — the developmental window differs from LMP-based advice.
Safe exercise
150 minutes/week of moderate activity — brisk walking, stationary cycling, prenatal yoga. Stop any exercise that leaves you unable to hold a conversation. At 4 weeks from conception, low-impact activity supports placental blood flow without stressing the fresh implantation.
Doctor visit checklist — week 4
- ✓Take a home pregnancy test; confirm with beta-hCG blood test
- ✓Note: 4 weeks from conception = 6 weeks LMP — clinic dating uses LMP
- ✓Confirm dating with crown-rump length at 8–13 weeks (±5 days accuracy)
Warning signs — call your provider immediately
- ⚠Heavy bleeding (soaking a pad in an hour)
- ⚠Severe abdominal pain that does not ease
- ⚠Fever above 38°C / 100.4°F
- ⚠Sudden loss of pregnancy symptoms + spotting
- ⚠Severe one-sided pain (ectopic pregnancy signal)
Week 4 — Frequently asked questions
Content aligned with ACOG dating criteria and Mayo Clinic conception timeline. Reviewed by Dr. Maria Rehman, MD (OB/GYN). This page is educational and does not replace personal medical advice — call your obstetrician for any concern.
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