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First trimester

6 weeks pregnant

At 6 weeks, the embryo is changing fast. Small buds that will become arms and legs appear, structures for the eyes and ears begin, and the heart beats with a regular rhythm. Nausea and tiredness are common for many people around now.

This page covers 6 weeks 0 days to 6 weeks 6 days (6+0 to 6+6), counted from the first day of the last period. Check how far along you are

Enter it to see the calendar dates of your week 6.

Botanical illustration of a lentil

About the size of a lentil

Early embryos are measured in millimetres; see below for what is forming now.

How your baby is developing

  • Small buds that will become the arms and legs start to grow. Tiny dents mark where the ears will be, and the structures that will become the eyes and mouth begin to form.1,2,3
  • The brain forms into five different areas, and some cranial nerves can be seen. Tissue that will become the spine and other bones begins to grow.2
  • The heart keeps growing and beats with a regular rhythm, and blood is pumping through the main vessels. Blood cells are taking shape as circulation begins.2,3
  • The liver and musculoskeletal system are developing. The embryo is covered with a thin layer of see-through skin and has a small tail, so some people think it looks like a tadpole.1
  • By around the end of this week, the embryo is roughly 6 millimeters long, according to the NHS.1

Changes you may notice

Everyone’s experience is different. You may notice some of these, or none.

  • Morning sickness can happen at any time of day, though it's often worse when you first wake up. Resting, eating small frequent meals of plain foods, sipping fluids, and trying ginger may help some people.1,4
  • Other common symptoms around now include tiredness, sore breasts, headaches, mood swings, needing to pee more often, more vaginal discharge, and bloating. Not everyone has them.1
  • Mild cramping a bit like period pain and light spotting can happen. Get advice about any bleeding, and call emergency services if bleeding comes with severe tummy pain, shoulder pain, or feeling faint or dizzy.1,5
  • Many people start to feel better after the first trimester. Talk to your midwife or doctor about anything that worries you.1

Care around this week

  • At a first prenatal visit, a US provider typically takes a health history and orders a set of blood tests, including your blood type and Rh factor, and checks for infections. A first-trimester ultrasound helps estimate your due date. In the UK, the booking appointment usually takes place between 8 and 12 weeks, and screening tests for infectious diseases are offered then.1,6,7
  • A heartbeat can sometimes be seen on a vaginal ultrasound around now. In the UK, you're unlikely to be offered a scan this early unless you've had IVF.1,2
  • If you can't keep food or fluids down, talk to your midwife or doctor. If lifestyle changes don't help with severe nausea, anti-sickness medicines that are safe in pregnancy are available.1,4

Questions to ask your provider

  • Will I have an ultrasound in the first trimester, and when?
  • Which blood tests will I have at my first visit?
  • What can I safely take for nausea if diet changes don't help?
  • Which symptoms should make me call you before my next appointment?
When to contact your provider straight away

Call 911 (US) or 999 (UK) in an emergency, such as heavy bleeding or bleeding with severe pain, a seizure, chest pain, or severe trouble breathing.8,9,10,11

These symptoms are not always serious, but each one needs prompt advice from your provider, midwife or maternity unit (or NHS 111 in the UK if you cannot reach them) rather than waiting for your next appointment, and it helps to tell them you are pregnant.

  • Vaginal bleeding or spotting at any stage of pregnancy. Call 911 or 999 if the bleeding is heavy or comes with severe belly pain, shoulder pain, or feeling faint or dizzy.5,10
  • Fluid leaking or gushing from your vagina, or discharge that is unusual for you. Get checked straight away if the fluid is greenish, colored or smells bad.10,11,12,13
  • Your baby moving less than usual, not moving, or a change in their usual pattern of movements. Call immediately, even in the middle of the night, and do not use a home Doppler to check yourself.10,14
  • A severe headache that does not go away with simple painkillers or gets worse, or sudden changes in your vision such as blurring or seeing flashing lights.8,10,11
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.8,10,11
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.8,10,15
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.13,15
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.10,11,13
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.10,11
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.16
  • Being sick so often that you cannot keep food or drink down, or signs of dehydration such as dark urine, peeing very little, or feeling dizzy.10,17
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.10,18

Questions about 6 weeks

Can you hear the baby's heartbeat at 6 weeks?

Sometimes it can be seen on a vaginal ultrasound around now, but often it can't be heard or seen until at least 6 to 7 weeks. Ask your provider what to expect at your first scan.1,6

How long does morning sickness last?

It usually clears up by weeks 16 to 20, and many people feel better after the first trimester. It doesn't put the baby at increased risk, but get help if you can't keep food or fluids down.1,4

Sources

  1. 6 weeks pregnant guideNHS Best Start in Life
  2. Fetal developmentUS National Library of Medicine
  3. Fetal development: week-by-week stages of pregnancyCleveland Clinic
  4. Vomiting and morning sicknessNHS (England)
  5. Vaginal bleeding in pregnancyNHS (England)
  6. Prenatal care in your first trimesterUS National Library of Medicine
  7. Your antenatal appointmentsNHS (England)
  8. Pre-eclampsiaNHS (England)
  9. Epilepsy and pregnancyNHS (England)
  10. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  11. Pregnancy symptoms you need to get help forNHS (England)
  12. Signs of going into labourNHS Best Start in Life
  13. Premature labour and birthNHS (England)
  14. Your baby's movementsNHS (England)
  15. Stomach pain in pregnancyNHS (England)
  16. Itching in pregnancyNHS (England)
  17. Severe vomiting in pregnancyNHS (England)
  18. Depression in pregnancyNHS (England)

Links checked November 12, 2026. Citing a source does not mean it endorses this site.

Written from the sources above and checked against them on 2026-11-12. Not reviewed by a clinician. Our editorial policy