First Trimester
The most transformative 13 weeks of your body's life - And often the hardest. Here's what's actually happening, what's normal, and what to do first in Singapore.
What's Happening: Weeks 1–13
The first trimester runs from your last menstrual period (LMP) to the end of week 13. Your body undergoes more hormonal change in these 13 weeks than at almost any other point in life. Use our due date calculator to confirm your estimated delivery date and trimester progress tracker to see how far along you are.
Weeks 1–2: Before Conception
Baby
Egg matures and is released at ovulation (usually Day 14). Fertilisation occurs in the fallopian tube.
Your Body
Hormone changes begin before you even know you're pregnant. LH surge triggers ovulation.
Week 3: Fertilisation & Implantation
Baby
Zygote divides as it travels to the uterus. Blastocyst implants into the uterine lining around Day 6–10.
Your Body
Implantation may cause light spotting (normal). hCG starts rising - Home tests can detect from Day 10–14.
Week 4–5: Embryo Forms
Baby
Three cell layers form (ectoderm, mesoderm, endoderm) that will become every organ. Neural tube begins closing. Heart starts beating by Week 5.
Your Body
Missed period. hCG doubles every 48–72 hours. Progesterone surges - Fatigue, breast tenderness, nausea begin.
Week 6–8: Major Organ Development
Baby
Heart chambers form. Arms and leg buds appear. Eyes, ears, and face begin forming. All major organs are in rough form by Week 8.
Your Body
Morning sickness peaks. Uterus grows to orange size. Frequent urination as kidneys filter more. Smell sensitivity intensifies.
Week 9–10: Embryo → Fetus
Baby
Officially called a fetus from Week 10. Fingers and toes separate. Bones begin hardening. Genitals start forming (not visible on scan yet).
Your Body
Nausea may begin easing. Waistband feels tighter. Skin changes - Dryness, acne, or that 'glow'.
Week 11–12: Movement Begins
Baby
Baby moves - You can't feel it yet. Reflexes develop. Heartbeat clearly visible on ultrasound. Neck transparency measurable (NT scan).
Your Body
Uterus rises above pubic bone. Nausea often eases. Energy returns for many women.
Week 13: End of First Trimester
Baby
Baby is fully formed - Just needs to grow. Fingerprints are forming. Risk of miscarriage drops significantly after Week 12.
Your Body
Most symptoms ease. Bump may begin to show. Safe to announce for most families.
First Trimester Symptoms - What's Normal
Morning sickness
Affects 70–80% of pregnant women. Peaks at 6–10 weeks, typically eases by 14 weeks. Despite the name, it can occur any time of day.
What helps: Eat small, frequent meals. Ginger tea or ginger biscuits. Cold foods often better tolerated. Avoid lying down after eating.
Extreme fatigue
Progesterone is sedating. Your body is building a placenta. Blood volume increasing. All while functioning normally.
What helps: Rest without guilt. Prioritise sleep. Light walks help more than total bed rest. Tell your employer early if needed.
Breast tenderness
Oestrogen and progesterone stimulate breast tissue growth. Often the first symptom noticed - Before a missed period.
What helps: Supportive bra. Avoid under-wire if painful. This eases significantly by second trimester.
Frequent urination
hCG increases blood flow to the kidneys. Uterus begins pressing on the bladder as it grows.
What helps: Stay hydrated despite the urge. Reduce caffeine. Pelvic floor exercises now help long-term.
Food aversions & cravings
Thought to be protective - Aversions often target foods that could harm the embryo (alcohol, strong meat, coffee). Cravings are less well understood.
What helps: Trust your aversions. Eat what you can tolerate. Cravings for non-food items (pica) - Tell your doctor immediately.
Heightened sense of smell
Oestrogen amplifies olfactory sensitivity. May worsen nausea significantly.
What helps: Open windows. Avoid triggers. Ask colleagues not to eat at your desk if possible.
Constipation
Progesterone relaxes smooth muscle - Including the intestines. Slows digestion significantly.
What helps: Increase fibre and water intake. Prune juice. Gentle walking. Tell your doctor before taking any laxatives.
Light spotting
Implantation bleeding (Week 3–4) is common and normal. Some women also spot after a Pap smear or sex.
What helps: Any bleeding with pain, heavy bleeding, or clots - Seek medical review immediately.
Hyperemesis Gravidarum (HG) - When Nausea Is Severe
HG affects 1–3% of pregnant women. It is not ordinary morning sickness. Signs: unable to keep any food or liquid down for more than 24 hours, vomiting more than 3–4 times per day, losing weight, dark urine or no urination, feeling faint.
Go to A&E or your polyclinic immediately. HG requires IV fluids and anti-nausea medication. It is a medical condition - Not a mental strength issue. KKH has specialist obstetric services for HG management.
First Appointments in Singapore
First Antenatal Visit
Confirmation of pregnancy (urine + blood hCG), dating, medical history, blood panel (blood type, FBC, rubella immunity, Hep B, HIV, syphilis, thalassaemia screen). Urine test. Blood pressure baseline.
Early Viability Scan
Transvaginal or transabdominal scan to confirm intrauterine pregnancy, heartbeat, and dating. Not always included in first polyclinic visit - May need a referral.
Nuchal Translucency (NT) Scan + OSCAR/NIPT
Measures fluid at back of baby's neck. Combined with blood tests to screen for Down syndrome (T21), Edwards syndrome (T18), Patau syndrome (T13). Optional - Discuss with your doctor.
First Trimester Review
Review of scan and blood test results. Discuss results and next steps. Prescription of supplements if not already on. Begin discussion of birth choices.
First Trimester Screening Tests
Wondering what OSCAR, NIPT, and the anomaly scan involve? Our pregnancy FAQ covers each test in detail.
| Test | When | What It Detects | Type |
|---|---|---|---|
| Urine pregnancy test | Week 4–5 | Confirms pregnancy (hCG) | Screening |
| Blood hCG + progesterone | Week 5–8 | Confirms viability, rules out ectopic | Screening |
| Full blood count (FBC) | Week 6–8 | Anaemia, platelet levels | Routine |
| Blood group & Rh factor | Week 6–8 | Rh incompatibility risk | Routine |
| Rubella immunity | Week 6–8 | Immunity status - No treatment in pregnancy | Routine |
| Hepatitis B surface antigen | Week 6–8 | Maternal infection - Affects newborn vaccination | Routine |
| HIV, syphilis | Week 6–8 | Maternal infection - Treatment prevents transmission | Routine |
| Thalassaemia screen | Week 6–8 | Carrier status - Partner tested if positive | Routine |
| NT scan (ultrasound) | Week 11–13⁺⁶ | Chromosomal anomalies (T21/T18/T13) | Screening |
| OSCAR blood test | Week 11–13⁺⁶ | Combined with NT for T21/T18/T13 risk | Screening |
| NIPT (cfDNA) | Week 10 onwards | Chromosomal anomalies - High sensitivity/specificity | Optional |
Nutrition in the First Trimester
Caloric increase is minimal in the first trimester - Roughly 100–200 extra kcal/day (a banana and a handful of nuts). The focus is on nutrient quality, not quantity. Use our nutritional requirement calculator for personalised guidance. Most women struggle to eat well due to nausea - Do the best you can.
Folic acid (folate)
Prevents neural tube defects (spina bifida). Critical in Weeks 3–4 when the neural tube closes - Often before a missed period. See our <a href="/tools/prenatal-vitamin-calculator/" class="text-primary underline hover:no-underline font-medium">prenatal vitamin calculator</a> to check your supplement doses.
Sources: Supplement: 400mcg/day (or 5mg if previous NTD or on anti-epileptics). Food: dark leafy greens, legumes, fortified cereals.
Singapore note: HPB recommends starting before conception. Most antenatal vitamins contain 400–800mcg.
Iron
Blood volume increases 50% by end of pregnancy. Iron supports this and prevents anaemia - Common in Singapore, especially among Indian and Malay women.
Sources: Supplement: 30–60mg elemental iron/day if anaemic. Food: red meat, tofu, tempeh, dark leafy vegetables, fortified cereals.
Singapore note: Take iron with vitamin C to enhance absorption. Avoid tea/coffee within 1hr of iron supplement.
Iodine
Essential for foetal brain and thyroid development. Often overlooked.
Sources: Supplement: 150mcg/day. Food: seaweed (in moderation), dairy, eggs, iodised salt.
Singapore note: Most Singapore prenatal vitamins include iodine. Check the label.
Calcium
Bone and teeth development. If intake is low, foetus draws from maternal bone stores.
Sources: Supplement: 1,000mg/day if dietary intake is low. Food: dairy, fortified soy milk, tofu (made with calcium sulphate), ikan bilis.
Singapore note: Ikan bilis is an excellent local source - Often overlooked. 100g provides ~800mg calcium.
DHA (omega-3)
Foetal brain and eye development. Most beneficial in T2/T3 but establish early.
Sources: Supplement: 200–300mg DHA/day. Food: salmon, sardines, mackerel, fortified eggs.
Singapore note: Many pregnant women in Singapore avoid fish due to mercury concerns - Opt for small oily fish (sardines, salmon) and supplement.
What to Avoid in the First Trimester
| Category | Avoid | Why | Safe Alternatives |
|---|---|---|---|
| Alcohol | All alcohol - No safe dose established | Associated with foetal alcohol spectrum disorder. Risk is highest in first trimester when organs form. | Sparkling water, mocktails, dealcoholised drinks |
| Caffeine | More than 200mg/day (~2 flat whites) | Higher doses linked to miscarriage and low birth weight. One coffee/day is generally considered safe. | Decaf coffee, rooibos tea, herbal infusions (ginger, peppermint safe) |
| Raw/undercooked fish | Sashimi, raw oysters, raw sushi | Listeria, salmonella, anisakis risk. Especially dangerous in pregnancy. | Cooked sushi rolls, tamago, vegetable maki, cooked prawns |
| High-mercury fish | Shark, swordfish, king mackerel, bigeye tuna | Mercury accumulates in neural tissue. Foetal brain is vulnerable. | Salmon, sardines, canned light tuna (limited), prawns, tilapia |
| Unpasteurised dairy | Raw milk, soft unpasteurised cheeses | Listeria risk - Listeria crosses the placenta and is dangerous to the foetus. | Pasteurised dairy, hard cheeses (cheddar, parmesan), cooked brie/camembert |
| Deli meats (unheated) | Cold cuts, luncheon meat, ham straight from the packet | Listeria contamination risk | Heat to steaming before eating, or avoid entirely |
| Vitamin A supplements (retinol) | High-dose retinol supplements (not beta-carotene) | Teratogenic in high doses (liver, high-dose supplements) | Prenatal vitamins with beta-carotene instead of retinol |
| Recreational drugs / smoking | All - No safe level | Associated with miscarriage, preterm birth, IUGR, stillbirth, SIDS | Speak to your doctor for cessation support - No judgement |
Traditional Confinement Herbs - First Trimester
Dong quai (当归)
Commonly used in TCM for blood circulation. Contains coumarin compounds - May stimulate uterine contractions.
Ginger (姜)
Anti-nausea properties well-studied. Considered generally safe at culinary doses.
Red dates (红枣)
Iron and antioxidants. Used in many tonic soups. Likely safe at culinary amounts.
Fenugreek seeds
Used in Malay confinement foods. May stimulate uterine contractions in high doses.
Longan (龙眼)
Considered 'heaty' in TCM - Traditionally cautioned against in first trimester.
Papaya (raw/unripe)
Unripe papaya contains papain and latex - Potentially uterotonic. Ripe papaya is safe.
Emotional Health in the First Trimester
Anxiety about miscarriage
First trimester miscarriage affects ~10–20% of known pregnancies - But 80%+ of these are chromosomal and not preventable. The anxiety is valid and very common.
Knowing the statistics helps some women. Avoid reading forums obsessively. One ultrasound at a time.
Emotional numbness or disbelief
Common - Especially with a positive test before any physical symptoms. The brain processes abstract information slowly.
Normal. No pressure to feel a particular way. Many parents don't feel 'connected' until they see the heartbeat or feel movement.
Relationship tension
Partners often process pregnancy very differently. Fear, excitement, financial stress, and identity shifts all hit differently.
Early, honest communication about fears - Not just logistics. Couples counselling is not a sign of failure.
Work stress and concealment
Singapore work culture can make it hard to manage symptoms while concealing pregnancy before 12 weeks.
You are not legally required to disclose before 12 weeks. Many women tell their direct manager early for support. Know your <a href="/faq/maternity-leave-singapore/" class="text-primary underline hover:no-underline font-medium">maternity leave eligibility</a> and workplace rights.
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