Pregnancy Week 3
Your baby is the size of a Pea - 0.1 cm
Your Baby at Week 3
Development highlights
- The embryo implants fully into the uterine lining
- The placenta begins forming - Your baby's life-support system
- hCG (pregnancy hormone) starts being produced and rises rapidly
- Three germ layers form: ectoderm, mesoderm, endoderm - All future structures arise from these
Source: WHO Child Growth Standards; embryology references from Moore & Persaud.
Your Body in Week 3
The first trimester is driven by rapidly rising hCG and progesterone. These hormones are essential for maintaining the pregnancy but cause most of the symptoms you're feeling. They typically peak around weeks 8–10 and start easing toward the end of week 12. Read more in the First Trimester Guide →
Common symptoms this week
Week 3 Checklist
- Take a home pregnancy test - HCG is now detectable in urine
- Book your first antenatal appointment (aim for week 8–10)
- Switch from ibuprofen to paracetamol if you need pain relief
- Tell your employer if your work involves hazardous chemicals or radiation
Vitamin D supports placental development. Singapore sunshine helps but indoor work and SPF use mean deficiency is common. Consider 400–600 IU daily.
Book via HealthHub app, your hospital's antenatal clinic, or your private OB. Bring your referral letter and NRIC.
Baby's Body Systems Development
How far along each major system is at week 3. Development is continuous - The chart shows when each system is actively forming and when it reaches maturity.
First Trimester: Key Milestones & Screenings
The first trimester is the most critical period for fetal development. All major organs form between weeks 3–13. Most miscarriages (about 80%) also occur in this period - This is why many couples wait until week 12 to announce. Key screening tests are done now to establish your due date and check for chromosomal conditions.
Confirms gestational age and heartbeat. Performed at KKH, NUH, or your private OB.
Learn more →Nuchal Translucency screening for chromosomal conditions. Pairs with blood test.
Learn more →Non-invasive prenatal test - More sensitive than OSCAR. Blood test, not covered by Medisave.
Learn more →Week-by-week: what forms when
| Weeks | Key development | Action |
|---|---|---|
| Wk 1–2 | Fertilisation, implantation, hCG begins | Start folic acid 400–800 mcg daily |
| Wk 3–4 | Neural tube closes, heart begins beating | Book first antenatal appointment |
| Wk 5–6 | Brain, limbs, facial features form | Dating scan booking, NIPT discussion |
| Wk 7–8 | All organs present, embryo becomes fetus | Dating scan - Hear the heartbeat |
| Wk 9–10 | Kidneys produce urine, bones begin | Book NT scan for 11–13 weeks |
| Wk 11–13 | NT scan, fingerprints form, sex organs | NT/OSCAR screening, baby bonus registration |
Frequently Asked Questions - Week 3
Yes - Many women have very few or no obvious symptoms in the first weeks. The absence of nausea, sore breasts, or fatigue doesn't mean anything is wrong. Every pregnancy is different. Symptoms typically appear between weeks 5–8 as hCG levels rise. If you're concerned, a blood hCG test from your GP can confirm your pregnancy is progressing.
In Singapore, the dating scan is typically done at 8–10 weeks. It confirms how far along you are, checks the heartbeat, and rules out ectopic pregnancy. The Nuchal Translucency (NT) scan, which screens for chromosomal conditions, is done between weeks 11–13. Both are available at KKH, NUH, Thomson Medical, and private OB clinics.
Focus on folic acid (400–800 mcg daily), iron-rich foods (red meat, lentils, spinach), calcium (dairy, tofu), and protein (eggs, fish, chicken). Avoid raw fish and shellfish, unpasteurised dairy, deli meats, and raw sprouts. If nausea makes eating difficult, eat small amounts frequently - Crackers, plain toast, bananas, and ginger are often well-tolerated.
Week 3 at a glance
Pregnancy Tools
Singapore Resources
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