First Trimester
4 Weeks Pregnant
Tiny but mighty! Your baby is just beginning to form.
🌱
Your baby is the size of a Poppy seed
0.2 cm
Crown-Rump Length
0.01 g
Approximate Weight
Week 1Week 13 — End of Trimester 1Week 27Week 42
🧒 Baby's Development This Week
At week 4, the blastocyst has successfully implanted into your uterine wall and is now technically an embryo. It's about the size of a poppy seed, but incredible things are happening: it's splitting into two layers, one that will become the baby and another that will form the placenta. This is the moment when the neural tube, which will become the brain and spine, begins to form.
- Major organ systems are forming.
- Reflexes are developing.
- Facial features become more distinct.
- Bones are hardening.
- Nervous system matures.
🤰 Your Symptoms at Week 4
You might notice a missed period this week, which is often the first big clue of pregnancy. Some women experience 'implantation bleeding'—light spotting that can be mistaken for a period—as well as early signs like bloating and breast tenderness as your pregnancy hormones, like hCG, begin to rise rapidly.
Fatigue
Rest when possible.
moderate
Rest when possible.
moderate
Nausea
Eat small, frequent meals.
mild
Eat small, frequent meals.
mild
Breast tenderness
Wear a supportive bra.
mild
Wear a supportive bra.
mild
Frequent urination
Stay hydrated but limit evening fluids.
moderate
Stay hydrated but limit evening fluids.
moderate
Mood swings
Talk to your partner or friends.
mild
Talk to your partner or friends.
mild
Body Changes
- Uterus is expanding.
- Blood volume is increasing.
- Skin changes may occur.
When to Call Your Doctor
- Severe abdominal pain or cramping
- Heavy bleeding or spotting
- Severe dizziness or fainting
✅ Week 4 Checklist
- Take prenatal vitaminsEssential
- Drink plenty of waterEssential
- Eat a balanced dietRecommended
- Exercise moderatelyRecommended
- RestEssential
❓ Frequently Asked Questions
Is it normal to feel tired?
Yes, fatigue is very common.
What should I be eating?
A balanced diet with plenty of fruits and vegetables.
Can I exercise?
Yes, moderate exercise is generally safe and beneficial.
When will I feel the baby move?
Usually between 16 and 25 weeks.
How much weight should I gain?
It depends on your pre-pregnancy BMI. Ask your doctor.
👩⚕️
Reviewed by Dr. Sarah Johnson, OB/GYNLast reviewed May 2024
Sources
- American College of Obstetricians and Gynecologists (ACOG)
- Intergrowth-21st Fetal Growth Standards
⚕️ Medical Disclaimer: This content is reviewed by medical professionals but is for informational purposes only. Always consult your healthcare provider for personalized guidance about your pregnancy.