Pregnancy Week by Week
From the moment of conception to birth - What's happening to your baby and your body every single week. Singapore prenatal schedules, growth charts, and symptom timelines.
Pregnancy by the Numbers
- Positive test typically at week 4–5
- Heart beating by week 6
- Morning sickness peaks weeks 6–9
- OSCAR screen at weeks 11–14
- Miscarriage risk drops sharply after week 12
- Energy typically returns
- Quickening (first movements) weeks 16–22
- Anomaly scan at weeks 18–22
- Glucose tolerance test weeks 24–28
- Baby's sex visible on scan
- Baby gains most weight now (28g/day at peak)
- Group B Strep swab at week 36
- Baby drops (lightening) at weeks 36–38
- Braxton Hicks contractions increase
- Full term = 37 weeks
Baby Size & Growth: Week by Week
Crown-to-rump length (CRL) for weeks 4–20; crown-to-heel for weeks 20–40. Weight is approximate based on ultrasound estimation.
Baby Length Progression (cm)
Complete Growth Reference Table
| Week | Size | Length | Weight | Key Development |
|---|---|---|---|---|
| 4 | Poppy seed | 0.2 cm | <1g | Implantation complete. Amniotic sac forming. |
| 5 | Sesame seed | 0.4 cm | <1g | Heart tube forms. Neural tube closing. |
| 6 | Sweet pea | 0.6 cm | <1g | Heartbeat detectable on ultrasound. |
| 7 | Blueberry | 1.0 cm | <1g | Brain divides into 5 regions. Arm and leg buds. |
| 8 | Raspberry | 1.6 cm | 1g | Fingers and toes forming. Eyes developing. |
| 9 | Grape | 2.3 cm | 2g | Embryo now called a fetus. Joints forming. |
| 10 | Kumquat | 3.1 cm | 4g | External genitalia beginning to form. |
| 11 | Fig | 4.1 cm | 7g | All major organ systems present. Fingernails. |
| 12 | Lime | 5.4 cm | 14g | Reflexes developing. Can open and close fist. |
| 13 | Peapod | 7.4 cm | 23g | Fingerprints forming. Intestines moving into body. |
| 14 | Lemon | 8.7 cm | 43g | Sex organs identifiable. Squinting, grimacing. |
| 16 | Avocado | 11.6 cm | 100g | Skeleton hardening. May feel first movements. |
| 18 | Sweet potato | 14.2 cm | 190g | Ears positioned. Yawning, hiccupping. |
| 20 | Banana | 25.6 cm | 300g | Halfway point. Vernix caseosa coating skin. |
| 22 | Papaya | 27.8 cm | 430g | Eyebrows visible. Grip strength developing. |
| 24 | Corn | 30.0 cm | 600g | Viability milestone. Lungs producing surfactant. |
| 26 | Lettuce head | 35.6 cm | 760g | Eyes opening. Brain developing rapidly. |
| 28 | Cauliflower | 37.6 cm | 1,005g | REM sleep cycles begin. Turning head-down. |
| 30 | Cucumber | 39.9 cm | 1,300g | Brain has billions of neurons. Lanugo disappearing. |
| 32 | Squash | 42.4 cm | 1,702g | Practicing breathing. Eyes detect light. |
| 34 | Butternut squash | 45.0 cm | 2,100g | Fingernails reach fingertips. CNS maturing. |
| 36 | Swiss chard | 47.4 cm | 2,622g | Lungs nearly mature. GBS swab this week. |
| 38 | Leek | 49.8 cm | 3,100g | Full term. Skull bones not yet fused. |
| 40 | Watermelon | 51.2 cm | 3,400g | Due date. Labour imminent or already begun. |
Fetal Development by Body System
Each organ system has its own critical development window. This is why first-trimester exposures (medications, infections, alcohol) carry the highest risk - The foundation is laid early.
Heart tube forms week 3–4; 4-chamber heart by week 7; heartbeat detectable on ultrasound week 6
Heart rate ~140–160 bpm; blood vessels fully formed; umbilical cord blood flow established
Heart rate slows slightly as nervous system matures; prepares for transition to air breathing
Neural tube closes by week 4 (critical folic acid window); brain divides into regions by week 7
100 billion neurons forming; myelin sheath beginning; sensory pathways connecting by week 24
Massive brain growth; cortical folding; REM sleep cycles begin; brain doubles in size in T3
Lung buds form by week 4; branching begins; but lungs are solid tissue - Not functional
Lung branching complete by week 24; surfactant production begins (viability milestone)
Surfactant matures (critical for breathing after birth); practice breathing movements; 36+ weeks lungs nearly ready
Limb buds appear week 4; cartilage skeleton forming; fingers and toes distinct by week 8
Cartilage replaced by bone (ossification); muscle control developing; baby moves deliberately
Bone density increasing; skull remains soft for birth; subcutaneous fat depositing rapidly
Gut tube forming; intestines initially outside body (herniate into umbilical cord); return by week 11
Swallowing amniotic fluid; kidneys producing urine; meconium accumulating in bowel
Digestive enzymes maturing; gut bacteria will colonise at birth; meconium ready to pass
Skin transparent; eyes forming from brain outgrowths; ears at neck level, migrating up
Vernix caseosa coating; lanugo hair covering; eyes complete; can hear by week 18
Lanugo disappearing; vernix thicker; fat depositing under skin; fingerprints set by week 24
Gonads appear week 5; indifferent until week 7; sex determination begins
External genitalia identifiable on scan by week 14–16; gonads descending
Testes fully descended in males by week 36; ovaries and uterus fully formed in females
Symptom Intensity by Trimester
Intensity shown as: none · mild · moderate · peak. See full symptoms guide →
| Symptom | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 24 | 28 | 32 | 36 | 40 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Nausea / vomiting | ||||||||||||||
| Fatigue | ||||||||||||||
| Breast tenderness | ||||||||||||||
| Food aversions | ||||||||||||||
| Heartburn / reflux | ||||||||||||||
| Constipation | ||||||||||||||
| Back pain | ||||||||||||||
| Round ligament pain | ||||||||||||||
| Swelling (oedema) | ||||||||||||||
| Braxton Hicks | ||||||||||||||
| Frequent urination | ||||||||||||||
| Leg cramps | ||||||||||||||
| Shortness of breath | ||||||||||||||
| Pelvic pressure | ||||||||||||||
| Week → | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 24 | 28 | 32 | 36 | 40 |
Singapore Prenatal Screening Timeline
Based on KKH and MOH guidelines. Private clinic timelines may vary slightly - Always confirm with your obstetrician.
| Week | Test / Appointment | What It Checks | Cost (approx.) |
|---|---|---|---|
| Wk 8–10 | First antenatal booking visit | Blood group, rubella immunity, HepB carrier, syphilis, HIV, iron, urine culture | Subsidised at polyclinic; $150–300 private |
| Wk 11–14 | OSCAR (Combined first-trimester screening) | Nuchal translucency scan + blood test → chromosomal risk estimate | ~$200 public; $500–800 private |
| Wk 11–14 | NIPT (optional, out-of-pocket) | Cell-free fetal DNA in maternal blood. Screens T21, T18, T13 and sex chromosomes. | $800–2,000 at private labs |
| Wk 18–22 | Detailed anomaly scan (20-week scan) | Full fetal anatomy, heart structures, brain, spine, limbs, placenta, fluid | Included in public package; $300–500 private |
| Wk 24–28 | OGTT - Oral glucose tolerance test | Gestational diabetes - 2-hour test after 75g glucose load | Included in antenatal package |
| Wk 28–32 | Growth scan + Doppler | Estimated fetal weight, growth percentile, umbilical and uterine Doppler blood flow | $150–300 private |
| Wk 36 | Group B Strep (GBS) swab | Vaginal/rectal swab for GBS bacteria - Treated with IV penicillin during labour | Included |
| Wk 36+ | CTG (cardiotocography) | Fetal heart rate monitoring, contraction patterns | At each late visit or on request |
| Wk 38–40 | Biophysical profile (BPP) | 5-part wellbeing score: breathing, movement, tone, fluid, CTG | $200–400 if indicated |
Medisave can be used for ultrasound scans and delivery. NIPT is not Medisave-claimable. Confirm with your obstetrician or hospital billing.
Recommended Weight Gain During Pregnancy
Based on IOM 2009 guidelines, used by Singapore hospitals. Use our Weight Gain Calculator → for personalised tracking.
Where Does the Weight Go? (at 40 weeks, normal BMI)
Key Milestones at a Glance
| Milestone | Typical Week | Notes |
|---|---|---|
| Positive pregnancy test | Week 4–5 | hCG detectable 10+ days after ovulation. Digital tests confirm. |
| Heartbeat on ultrasound | Week 6 | Vaginal ultrasound required this early - Transabdominal may not detect yet. |
| Nuchal translucency scan | Weeks 11–14 | Combined with blood test (OSCAR) for Down syndrome risk. |
| End of high miscarriage risk period | Week 12 | Risk drops to ~1% after week 12. Most women announce at this point. |
| First movements (quickening) | Weeks 16–22 | Earlier for second pregnancies. May feel like flutters or bubbles at first. |
| Anomaly scan | Weeks 18–22 | Checks all major structures, heart chambers, spine, limbs, placenta. |
| Fetal viability milestone | Week 24 | With intensive NICU care, survival possible. 85% survival rate by week 28. |
| Glucose tolerance test (OGTT) | Weeks 24–28 | Screens for gestational diabetes. 2-hour test after 75g glucose. |
| Third trimester begins | Week 28 | Baby now gains ~200g/week. Kick counting becomes important. |
| Group B Strep swab | Week 36 | Vaginal/rectal swab. GBS positive: IV penicillin during labour. |
| Baby 'drops' (lightening) | Weeks 36–38 | Head engages in pelvis. May breathe easier; more pelvic pressure. |
| Full term | Week 37 | Birth now safe. Lungs, brain, and body ready for outside world. |
| Due date (EDD) | Week 40 | Only 5% of babies born exactly on due date. Normal range 38–42 weeks. |
Deep Dive: Trimester Guides
Morning sickness, OSCAR screening, what's safe to eat, and surviving the most anxious weeks.
The 'golden period' - Anomaly scan, feeling movements, glucose test, and body changes.
Birth prep, GBS test, hospital bag, signs of labour, and what happens after 40 weeks.
Jump to Your Week
First Trimester
Weeks 1–13 · Formation & organogenesis
Second Trimester
Weeks 14–27 · Growth & the golden period
Third Trimester
Weeks 28–42 · Maturation & birth preparation
Antenatal Blood Test Reference
Normal ranges used in Singapore hospitals (may vary slightly by lab). Results outside range warrant discussion - Not immediate alarm.
| Test | When Done | Normal Range (pregnant) | What It Detects |
|---|---|---|---|
| Haemoglobin (Hb) | Booking + 28w | ≥ 11.0 g/dL | Anaemia - Common in pregnancy, especially T2–T3 |
| Blood group + Rh | Booking | N/A | Rhesus incompatibility - Rh– mothers need anti-D injection |
| Rubella IgG | Booking | ≥ 15 IU/mL = immune | Rubella immunity - Risk of fetal defects if primary infection in T1 |
| Hepatitis B sAg | Booking | Negative | HBsAg+ mothers: baby receives HBIG + vaccine at birth |
| Syphilis (VDRL/RPR) | Booking | Non-reactive | Congenital syphilis - Treatable with penicillin in pregnancy |
| HIV antibody | Booking | Negative | Vertical transmission preventable with ART in pregnancy |
| Urine culture | Booking | No growth | Asymptomatic bacteriuria → treated to prevent pyelonephritis |
| Fasting glucose / OGTT | 24–28w | Fasting < 5.1 mmol/L; 2hr < 8.5 mmol/L | Gestational diabetes mellitus (GDM) |
| Full blood count (FBC) | Booking + 28w + 36w | Hb ≥ 11, Plt > 150,000 | Anaemia, platelet disorders |
| Thyroid (TSH) | If symptoms / history | 0.1–2.5 mIU/L (T1); 0.2–3.0 (T2–T3) | Hypothyroidism - Affects fetal brain development if untreated |