Trimester 1
Week 4
Your baby is about the size of a sesame seed.
Length: 0.2 cm · Weight: <1 g
Common this week: Missed period, Breast tenderness, Fatigue, Nausea, Frequent urination.
Baby development
- The embryo has implanted fully in the uterine lining.
- Three cell layers form: ectoderm (skin/nervous system), mesoderm (muscles/bones), endoderm (organs).
- The amniotic sac and yolk sac begin to develop.
- hCG levels are rising rapidly — a pregnancy test will likely be positive.
Changes for you
- Missed period — the first noticeable sign for most women.
- Breast tenderness or tingling may begin.
- Mild nausea may start for some women.
- Fatigue can set in as progesterone rises.
Tips
- Take a home pregnancy test if your period is late.
- Book an appointment with your GP to confirm the pregnancy and get a referral to an obstetrician or midwife.
- Continue folic acid; your GP may recommend a pregnancy multivitamin.
- Avoid ibuprofen and NSAIDs — paracetamol is generally considered safe, but always consult your healthcare provider.
Appointments
- Book a GP appointment to confirm pregnancy and discuss antenatal care options.
Warning signs
- Heavy bleeding
- Severe cramping
- Positive test followed by period (may indicate early loss)
Australian notes
- In Australia, you can choose shared care (GP + hospital), midwife-led care, or private obstetrician care.
- Medicare covers many antenatal visits — ask your GP about your Medicare card.
- The NSW Health Blue Book (Personal Health Record) is given to pregnant women at their first antenatal visit.