Your baby at 4 weeks
The embryo develops rapidly inside the uterus. A fluid-filled sac provides a protective environment.
Structures that support nourishment, including tissue that will form the placenta, are developing.
TRIMESTER 1 · WEEK 4
4 weeks pregnant
A tiny beginning.
What to expect at 4 weeks pregnant: your baby, your symptoms and this week’s reminders.
Symptoms at 4 weeks pregnant
- You may notice a missed period.
- Breast tenderness and tiredness may begin.
- Having no symptoms is also possible.
None of these symptoms is required. Symptoms alone cannot diagnose pregnancy or establish your baby’s wellbeing.
After a positive test, contact a healthcare professional to arrange pregnancy care.
Source for this week: NHS — Week 4
YOUR WEEK, YOUR JOURNEY
Explore another pregnancy week
Choose a week to explore your baby’s development and changes you may notice.
01 · FIRST TRIMESTERSmall beginnings
02 · SECOND TRIMESTERA growing connection
03 · THIRD TRIMESTERGetting closer to meeting
Sources and content note
This is source-based general information, not a substitute for a clinical assessment or individual care plan. The presence, absence or change of symptoms alone cannot establish pregnancy wellbeing. This content is not a personalised care plan reviewed by a healthcare professional.
This guide groups weeks 1–13 in the first trimester, 14–27 in the second, and 28 onwards in the third. Weeks refer to gestational age dated from the last menstrual period; clinical dating may differ.
- NHS — Pregnancy week by week
- ACOG — Fetal development and gestational age
- NHS — Your baby’s movements
- NHS — Pregnancy symptoms
Sources checked: 31 October 2026 · Illustrations are AI-generated conceptual drawings, not ultrasound or diagnostic images.