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.
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
How accurate is the Conception Calculator at week 4?
The calculator uses standard gestational-age arithmetic (LMP + 280 days for standard; egg retrieval + 266 days for IVF day-5). Ultrasound crown-rump length between weeks 8–13 is more accurate (±5 days) than LMP — adjust EDD accordingly if the scan differs by more than 7 days.
What size is my baby at week 4?
Approximately the size of a poppy seed — length 0.1 cm and weight 0 g. These are median values from ACOG dating criteria and Mayo Clinic conception timeline references.
Which symptoms are normal in week 4?
Implantation spotting possible (light pink/brown, 1–2 days). Home pregnancy test may turn positive at the end of the week. Every pregnancy is different — call your provider if anything on the warning-signs list appears.
Should I have an ultrasound at week 4?
Take a home pregnancy test; confirm with beta-hCG blood test. Routine scan windows are: dating (10–13w), anatomy (18–22w), growth (28–32w).
How much weight should I gain by week 4?
Approximately 0.6 kg cumulative if you started at a normal BMI (IOM guideline). Underweight mothers gain more; overweight mothers less.
4 weeks from conception is how many weeks pregnant?
4 weeks from conception = 6 weeks gestational (LMP-based). All clinical care uses LMP dating unless IVF or dating scan overrides.
Can I feel conception happening at week 4?
No — conception itself is not felt. Later pregnancy symptoms are hormone-driven, not conception-related.
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.