🌱 Antenatal Guide — Weeks 1–12

First Trimester Guide

The first trimester is the period of most rapid development — by week 12 your baby has all major organs formed. It is also the time of greatest miscarriage risk and the most important period for folate supplementation, registration for antenatal care, and first-line investigations.

Key Milestones

🌱 Weeks 1–4: Conception and implantation

The egg is fertilised and travels to the uterus, implanting around day 6–10. Most women do not know they are pregnant yet. The placenta begins forming, producing hCG (the hormone detected by pregnancy tests).

🌱 Weeks 5–6: Missed period and first positive test

A urine pregnancy test is reliable from the day of a missed period. A rising hCG level doubles every 48–72 hours in a healthy early pregnancy. At week 6, a transvaginal scan can detect the gestational sac and, from 6 weeks 3 days, often a fetal heartbeat.

🌱 Weeks 7–8: Heartbeat confirmed

The embryo is the size of a kidney bean (~1.6 cm). The fetal heartbeat (FHR 110–160 bpm) is reliably seen on TVS scan. Major organs — brain, heart, kidneys, spine — are beginning to form.

🌱 Weeks 10–12: First trimester screen

The nuchal translucency (NT) measurement is done between 11–14 weeks — an ultrasound measurement at the back of the baby's neck that, combined with blood markers (PAPP-A and β-HCG), screens for Down syndrome (trisomy 21) and other chromosomal conditions. CRL (crown-rump length) gives the most accurate gestational age dating at this stage.

Essential Tests & Scans

Urine Pregnancy Test

⏱ From day 1 of missed period

Detects hCG in urine. Reliable from the day of a missed period. A faint positive line is still positive — any line indicates pregnancy.

Transvaginal Scan (TVS)

⏱ Weeks 6–9

Confirms intrauterine pregnancy, detects heartbeat, identifies twins, dates the pregnancy, and excludes ectopic pregnancy (pregnancy outside the uterus — a medical emergency).

Dating Scan

⏱ Weeks 8–12

Crown-rump length (CRL) measured to calculate gestational age and expected due date (EDD) more accurately than LMP alone.

First Trimester Booking Blood Tests

⏱ Weeks 8–12

Full blood count (anaemia), blood group and Rhesus factor (Rhesus-negative mothers need anti-D), HIV (PMTCT), Hepatitis B (neonatal vaccination if mother positive), Syphilis (VDRL/TPHA — treatable and prevents congenital syphilis), rubella immunity, fasting glucose (early GDM screen for high-risk women), urine culture (asymptomatic bacteriuria causes premature labour).

Nuchal Translucency Scan + First Trimester Screen

⏱ Weeks 11–14

NT measurement combined with serum PAPP-A and β-HCG calculates individualised Down syndrome risk. A risk above 1:300 triggers referral for NIPT (non-invasive prenatal testing) or amniocentesis.

⚠️ Warning Signs — Seek Help Immediately

🚨 Heavy vaginal bleeding (heavier than a period) with or without pain — may indicate miscarriage or ectopic pregnancy
🚨 Severe one-sided pelvic pain with bleeding and a positive pregnancy test — possible ectopic pregnancy: go to emergency immediately
🚨 High fever above 38.5°C — infection during early pregnancy (rubella, listeria, CMV) carries significant fetal risk
🚨 Severe vomiting unable to keep any food or fluid down (hyperemesis gravidarum) — risk of dehydration and hospitalisation
🚨 No fetal heartbeat seen on scan after week 7 on a TVS — may indicate missed miscarriage; requires clinical review

Practical Tips for This Stage

Start folic acid immediately — before symptoms start ideally

Take 400 mcg folic acid daily from the day you start trying to conceive and continue until 12 weeks of pregnancy. Folic acid prevents neural tube defects (spina bifida) — which occur in weeks 3–4, before most women know they are pregnant. Women with a previous neural tube affected pregnancy or on certain medications need 5 mg/day.

Book your first antenatal appointment before 10 weeks. Early registration allows time for all first-trimester investigations, nuchal translucency scan, and early identification of risk factors. Late booking (after 20 weeks) means missing critical early screening windows.

Manage morning sickness safely

Nausea and vomiting in the first trimester affects 70–80% of women. Tips: small, frequent meals every 2–3 hours; cold or room-temperature foods are better tolerated than hot ones; ginger (tea or supplements) reduces nausea moderately; vitamin B6 (pyridoxine) 25 mg three times daily has good evidence for nausea reduction. Severe vomiting needs antiemetic prescription — do not suffer in silence.

Avoid alcohol, smoking, and certain medications

No alcohol is safe in pregnancy — all is potentially teratogenic. Stop smoking (increases miscarriage, placental abruption, and stillbirth risk). Avoid NSAIDs (ibuprofen, diclofenac) especially after 28 weeks. Paracetamol is safe for pain. Check any medication with your obstetrician before continuing.

Attend your partner — emotionally and practically

The first trimester is often emotionally isolating — fear of miscarriage means many couples delay telling family. The anxiety is normal. Build a support structure with your partner. Attend appointments together where possible.

Frequently Asked Questions

Is spotting in early pregnancy normal?

Light spotting around the time of expected implantation (5–6 weeks) or after a TVS is common and usually benign. Heavy bright-red bleeding, especially with cramping, is not normal and requires urgent assessment. Any bleeding in early pregnancy should be evaluated with a TVS to confirm the pregnancy is still intrauterine and the heartbeat is present.

How do I know if I am having a miscarriage?

Signs of miscarriage: heavy vaginal bleeding (heavier than a normal period), passage of tissue or clots, severe cramping, and sudden resolution of pregnancy symptoms (nausea, breast tenderness). A TVS scan confirms whether the pregnancy is continuing (heartbeat present) or miscarrying. Not all bleeding is miscarriage — but all significant bleeding needs evaluation.

Can I exercise during the first trimester?

Yes — moderate exercise is safe and beneficial. Continue your pre-pregnancy exercise routine at a comfortable intensity. Avoid contact sports, high-impact activities with fall risk, hot yoga, and scuba diving. If you were not exercising before, start with 20–30 minutes of walking daily. Exercise reduces gestational diabetes, excessive weight gain, back pain, and postpartum depression.

When should I tell people I am pregnant?

Medically, the risk of miscarriage falls significantly after the 12-week scan. Many couples choose to wait until after this scan before telling family and friends. However, this is a personal decision — some women benefit from telling trusted people earlier for emotional support, especially if experiencing significant symptoms or anxiety.