First Trimester
Week 4: Implantation is complete — you are officially pregnant.
Here's everything happening with your baby and your body this week.
Your baby is the size of a
Poppy seed
Length
0.04 in
Weight
< 1 g
Week
4 / 40
💡 Expert tip
Start folic acid (400–800 mcg daily) if you haven
🌱 Baby's development this week
- Embryo implants in uterine wall
- Amniotic sac forming
- Placenta beginning to develop
- Neural tube starting to form
Science fact
The neural tube — which becomes the brain and spinal cord — forms entirely in weeks 3–4. Folic acid prevents 70% of neural tube defects.
🤰 Your symptoms this week
Implantation cramping
feels like mild period cramps, normal
Light spotting
affects 25% of pregnancies, usually harmless
Fatigue
your body is producing progesterone at 10x normal levels
Rest when you can — your body is building a placenta. Iron-rich foods (spinach, lentils) help. Short walks boost energy.
💛 Changes in your body
- Missed period
- Early pregnancy test may turn positive
- Mild cramping or spotting possible
- Progesterone rises — may feel unusually tired
💙 Mental health this week
Anxiety about early pregnancy is extremely common. Sharing the news (even with one trusted person) can help reduce isolation.
🥗 Nutrition focus
- Folic acid 400–800 mcg/day
- Iron-rich foods (lentils, spinach)
- Stay hydrated — 8–10 glasses water
📅 Appointment / test
Schedule your first prenatal appointment for weeks 8–10 now.
✅ This week's checklist
Start prenatal vitamins with folic acid if not already
Avoid alcohol, smoking, raw fish, and soft cheeses
Calculate your due date (40 weeks from LMP)
Track your pregnancy week by week
Interactive guide · 40 weeks · Fruit size visualizations · Personalized tips
Open Week 4 in Interactive Guide → →