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Second trimester

18 weeks pregnant

At 18 weeks your baby's hearing, swallowing and sucking reflexes are developing, and there is plenty of wriggling. Some people feel a gentle fluttering for the first time around now. The anatomy scan is usually done between 18 and 22 weeks in the US and between 18 and 21 weeks in the UK.

This page covers 18 weeks 0 days to 18 weeks 6 days (18+0 to 18+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 18.

Botanical illustration of a bell pepper

About the size of a bell pepper

Typical estimated weight 225 g (8 oz) at 18+0, about 265 g (9 oz) by 18+6. This is the 50th centile; healthy babies commonly vary by about 12.7% either way.1

A reference value, not a measurement of your baby.

How your baby is developing

  • Hearing, swallowing and sucking reflexes are developing, and your baby wriggles and moves their arms and legs a lot.2
  • Fine, downy hair called lanugo is spreading over the skin, and your baby may have sleep and wake cycles. Loud noises might wake them.3,4
  • Bones continue to harden, and the skin is still thin and almost see-through.4
  • Your baby has been moving for a couple of months. Around now, some of those movements may become strong enough for you to notice.2

Changes you may notice

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

  • Blood pressure tends to drop slightly at this stage, so standing up slowly can help you avoid feeling dizzy.2
  • A dark line called the linea nigra may appear on your tummy. It is a normal change in skin pigment and usually fades a few months after the birth.2
  • Your breasts may have grown, especially in a first pregnancy, and a bigger bump can make you feel a little less coordinated.2
  • Some people feel a bubbling or fluttering inside for the first time around now. Many don't yet, and in a first pregnancy it's common not to feel movement until after 20 weeks.2,5,6
  • Energy often improves in the second trimester. If you're struggling with tiredness or other symptoms, speak to your midwife or doctor.2

Care around this week

  • In the US, the anatomy ultrasound is usually done between 18 and 22 weeks and looks at your baby's development in detail. UK: the 20-week screening scan is usually done between 18 and 21 weeks. It looks for 11 conditions and usually takes around 30 minutes.2,7,8
  • No scan can find every condition. If something is found, you may be offered more scans or tests and referred to a specialist. Having the scan is your choice.8
  • Once you are feeling regular movements, get to know your baby's usual pattern. If movements slow down, change or stop, contact your midwife or maternity unit straight away rather than waiting for your next appointment.5
  • UK: pregnant women get free NHS prescriptions and dental treatment with a maternity exemption certificate (MatEx). Ask your midwife, GP or health visitor for form FW8.2

Questions to ask your provider

  • When is my anatomy scan, and can I bring someone with me?
  • Can I choose whether or not to find out the baby's sex at the scan?
  • What happens if the scan shows something that needs a closer look?
  • I sometimes feel dizzy when I stand up. Is that something to watch?
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.9,10,11,12

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.11,13
  • 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.11,12,14,15
  • 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.5,11
  • 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.9,11,12
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.9,11,12
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.9,11,16
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.15,16
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.11,12,15
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.11,12
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.17
  • 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.11,18
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.11,19

Questions about 18 weeks

Can you find out the baby's sex at the 18-week scan?

Often, yes. The sonographer may be able to tell you, but some hospitals don't share this. Say before the scan if you would rather not know.2,8

What does the anatomy scan check?

It looks at your baby's development in detail, along with growth and the placenta. The NHS version screens for 11 conditions, but no scan can find every condition.2,8

Is it normal not to feel movement at 18 weeks?

Yes, many people haven't felt anything yet. First movements are usually felt between 16 and 24 weeks, and in a first pregnancy often after 20 weeks. Tell your midwife if you haven't felt movement by 24 weeks.5

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. 18 weeks pregnant guideNHS Best Start in Life
  3. Fetal development: week-by-week stages of pregnancyCleveland Clinic
  4. Fetal developmentUS National Library of Medicine
  5. Your baby's movementsNHS (England)
  6. Quickening in pregnancyCleveland Clinic
  7. Ultrasound ExamsAmerican College of Obstetricians and Gynecologists
  8. 20-week screening scanNHS (England)
  9. Pre-eclampsiaNHS (England)
  10. Epilepsy and pregnancyNHS (England)
  11. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  12. Pregnancy symptoms you need to get help forNHS (England)
  13. Vaginal bleeding in pregnancyNHS (England)
  14. Signs of going into labourNHS Best Start in Life
  15. Premature labour and birthNHS (England)
  16. Stomach pain in pregnancyNHS (England)
  17. Itching in pregnancyNHS (England)
  18. Severe vomiting in pregnancyNHS (England)
  19. 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