Week 4 Size: Poppy Seed
About the size of a tiny poppy seed.
Relative Visual Scale
Solid circle represents your baby's size. Dotted circle shows the full-term week 40 size threshold.
Baby's Development
The blastocyst is now officially an embryo. The cells are organizing into layers: one will form the baby, another the amniotic sac, and the third the placenta.
Weekly Milestones
- ✦ Positive Pregnancy Test Possible
- ✦ Embryo Formation
Your Body & Symptoms
Your missed period is the biggest indicator. A home pregnancy test can likely detect a positive result now. Your uterine lining is enriching to support the embryo.
Common Symptoms this Week
Doctor & Care Recommendations
- ✓ Take a home pregnancy test if your period is late.
- ✓ Schedule your first prenatal appointment (usually set for week 8 to 12).
- ✓ Limit caffeine intake to less than 200mg per day (about one 12oz cup of coffee).
PregWeeks
CHECKLISTUltimate Hospital Bag & Birth Plan
Print-Ready PDFThe Ultimate Hospital Bag Checklist & Birth Plan PDF
Prepare for labor with confidence. Our doctor-reviewed checklists ensure you don't forget any newborn or partner essentials in the hospital delivery room.
- ✓ Clinical OB-GYN Approved List: Separate checklists detailing exactly what mom, partner, and newborn baby require for a standard 3-day recovery stay.
- ✓ 10-Second Birth Preference Builder: Minimalist visual plan templates designed to help delivery nurses digest your labor choices instantly on check-in.
- ✓ 1-Click Offline Access: High-resolution, print-ready document formatted to download directly to your mobile device for offline reference in the clinic.
Weekly Health Guides & Resources
First Trimester Guide
Read comprehensive clinical milestones, screening checklists, and developmental guidelines for this phase.
Track & Relieve Symptoms
Learn why symptoms occur, home remedies, and clinical indicators for this week:
Food Safety Checklists
Verify safety statuses, listeria and mercury risks, and safe alternatives for:
Frequently Asked Questions: Week 4
Evidence-Based Clinical Sources for Week 4
PregWeeks is dedicated to medical transparency. Every milestone, symptom tip, and fetal development guideline for Week 4 is sourced directly from clinical guidelines published by leading obstetric authorities. Read more about our editorial methodology on our Medical Sources page.
Methods for Estimating Due Date (Committee Opinion No. 721)
ACOGOfficial clinical recommendations on calculating gestational age and due dates using last menstrual period (LMP) and ultrasound measurements.
View Clinical Guideline ↗Folic Acid Guidance to Prevent Neural Tube Defects
CDCPublic health guidelines on the daily recommended intake of prenatal folic acid (400 mcg) before and during early pregnancy.
View Clinical Guideline ↗Antenatal Care for a Positive Pregnancy Experience
WHOGlobal standard guidelines recommending early prenatal visits, nutritional counseling, and basic blood screening starting in the first trimester.
View Clinical Guideline ↗Get weekly pregnancy updates
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