Pregnancy Week 6: Baby's First Heartbeat, Morning Sickness, and What to Expect

The size of a pea — and a heartbeat just beginning Week 6 is when your embryo grows limb buds, and some parents see that first flicker of cardiac activity on an ultrasound.

At six weeks of pregnancy, your embryo is about 6 millimetres long — roughly the size of a pea. From the outside, very little has changed, but inside a remarkable transformation is underway: the heart is forming, limb buds are appearing, and the neural system is taking shape.

This article draws on NHS guidance [1], ACOG recommendations [2][4], WHO Antenatal Care guidelines [3], CDC folic acid guidance [6], and the Royal Thai College of Obstetricians and Gynaecologists [5].

Your baby at week 6

Your embryo is approximately 6 mm long — about the size and shape of a pea, according to the NHS [1].

Key developments happening now:

• Heart — a visible bump marks where the heart is forming; the heartbeat may be detectable by transvaginal ultrasound, though this is not routine unless you had IVF [1]
• Limb buds — tiny arm and leg buds are just beginning to emerge from the embryo's body
• Ear indentations — small dents where the outer ears will form are visible
• Brain and nervous system — the neural tube is closing; the brain is developing rapidly
• Liver and musculoskeletal system — these systems are beginning to organize
• Yolk sac — still present and supplying nutrients until the placenta takes over around weeks 9–10
• Gestational sac — visible on ultrasound; the embryo and yolk sac are nestled inside it
• Skin — the embryo is covered with a thin, transparent layer

Week 6 at a glance

Symptoms you may feel

Week 6 is often when pregnancy symptoms arrive in force, since hCG levels are now high and rising quickly.

Morning sickness

Despite its name, nausea can strike at any time of day. According to ACOG [2], about 75% of pregnant women experience nausea during the first trimester, with or without vomiting. Symptoms typically:

• Begin around weeks 5–6 and peak around week 9
• Ease in the second trimester for most women
• Are triggered by smells, certain foods, or an empty stomach

Other common symptoms at week 6

• Fatigue — deep, unusual tiredness from rising progesterone
• Tender, swollen breasts — glands are already preparing for lactation
• Frequent urination — hCG stimulates the kidneys to work harder
• Metallic taste — a distinctive sensation many women notice in early pregnancy
• Heightened sense of smell — foods that were once appealing may now cause nausea
• Mood swings — driven by rapid hormonal shifts

No symptoms at week 6 is also normal — not everyone has obvious signs at this stage.

Self-care in week 6

Folic acid is urgent

If you have not started folic acid, begin now. The CDC [6] and NHS [1] both recommend at least 400 mcg per day, starting before conception and continuing through at least the first 12 weeks of pregnancy. Folic acid significantly reduces the risk of neural tube defects (spina bifida, anencephaly) — conditions that develop in the earliest weeks of pregnancy.

Ask your doctor or pharmacist about the right dose for you — women with certain risk factors may need a higher amount.

Managing morning sickness

Per ACOG Practice Bulletin No. 189 [4]:

• Small, frequent meals — avoid an empty stomach, which worsens nausea
• Avoid trigger smells — step outside or away from strong food odors
• Sip fluids between meals — ginger tea or plain water
• Ginger — has clinical evidence supporting nausea relief
• Vitamin B6 (pyridoxine) — may help reduce symptoms; talk to your doctor before starting
• Rest — fatigue makes nausea worse; rest when you can

For severe nausea and vomiting that prevents you from keeping fluids down, contact your doctor. Hyperemesis Gravidarum (severe vomiting in pregnancy) affects about 0.3–3% of pregnancies and requires medical treatment.

Nutrition essentials

Per WHO Antenatal Care guidelines [3]:

• Folic acid — at least 400 mcg/day (see above)
• Iron — to prevent anemia; a prenatal vitamin typically covers this
• Varied diet — vegetables, fruits, protein, complex carbohydrates
• Water — at least 8 glasses a day; good hydration helps with nausea too

What to avoid

• Alcohol — no amount is safe during pregnancy
• Raw or undercooked meat and fish — risk of Listeria and Toxoplasma
• High-mercury fish — shark, swordfish, king mackerel, and certain tuna
• Unpasteurized cheeses and dairy — Listeria risk
• Caffeine — limit to under 200 mg/day (roughly 1 coffee)
• Liver and liver products — very high vitamin A, which can be harmful in excess

Prenatal care: when to book

WHO [3] recommends a first prenatal visit before 12 weeks. At week 6, this means you have a few weeks to schedule your booking appointment — don't delay past the first trimester.

What happens at the first visit

Your first prenatal visit typically includes:

• Ultrasound — confirms gestational age, number of embryos, and pregnancy location (to rule out ectopic pregnancy); heartbeat may be visible if transvaginal
• Blood work — blood type, Rh factor, complete blood count, blood glucose
• Infectious disease screening — HIV, syphilis, hepatitis B, rubella immunity
• Urinalysis — protein, glucose, infection
• Nutritional and BMI assessment
• Risk consultation — family history, chronic conditions, current medications

Prenatal care coverage in Thailand

Free prenatal care is available under Thailand's public health schemes [5]:

• 30-baht Universal Coverage scheme (บัตรทอง) via NHSO
• Social Security for insured employees
• Civil Service scheme for government employees and their families

When to seek care immediately

Contact your doctor or go to a hospital right away if you experience:

• Vaginal bleeding — more than light spotting
• Severe one-sided abdominal pain — possible sign of an ectopic pregnancy (a medical emergency)
• Shoulder-tip pain — pain at the tip of the shoulder, especially together with abdominal pain or bleeding, can indicate internal bleeding from a ruptured ectopic pregnancy
• Dizziness, lightheadedness, or fainting — particularly when combined with abdominal pain or bleeding, may signal internal blood loss
• Severe vomiting — unable to keep any fluids down; weight loss > 5% of pre-pregnancy weight (possible Hyperemesis Gravidarum)
• High fever > 38.5°C (101.3°F)
• Severe headache, blurred vision, or swelling — possible early pre-eclampsia signs

Week 6 is within the highest-risk period for miscarriage. If you have bleeding with cramping or pass tissue, seek care promptly.

Summary

Week 6 marks the beginning of visible embryonic structures and, for many women, the full onset of first-trimester symptoms.

Key actions this week:

1. Start folic acid now if not already taking it — at least 400 mcg/day per CDC [6]
2. Manage morning sickness with small frequent meals, ginger, and rest
3. Book your first prenatal visit for weeks 8–12 per WHO guidelines [3]
4. Avoid alcohol, raw fish, and high-mercury fish throughout pregnancy
5. Know the warning signs — bleeding with pain, severe vomiting, high fever

If anything worries you, reach out to your provider. Week 6 may feel relentless if morning sickness has arrived — but this phase is temporary, and you don't have to manage it alone.