First trimester
Pregnancy Week 4
Your baby is about the size of a poppy seed.
Size
poppy seed
Length
0.5 mm
Weight
< 0.001 g
Baby in week 4
The embryo is implanted. The amniotic sac and yolk sac form. The placenta begins to develop.
What you may notice this week
Possible missed period. Some early symptoms: tender breasts, light cramping, fatigue. Home pregnancy test can detect hCG now.
Tips for week 4
- Take a home pregnancy test
- Schedule your first prenatal appointment
- Avoid raw fish, soft cheeses, and deli meats
Tools that pair with this week
Due Date Calculator
Estimate your delivery date by last period or conception date. Naegele’s rule plus cycle adjustments.
Week Tracker
See exactly how many weeks and days pregnant you are, plus your trimester and key milestones.
Contraction Timer
Tap once to start, once to stop. Tracks duration, frequency, and pattern over time.
Ovulation Calculator
Find your fertile window based on your cycle length. Plan or avoid with confidence.
Baby Name Generator
Filter by origin, style, length, and starting letter. Boys, girls, and unisex.
Growth Percentile
Plot your baby’s weight, length, and head circumference against WHO percentile curves.