Pregnancy Due Date Calculator
Menu

Second trimester

20 weeks pregnant

At 20 weeks you are halfway through a 40-week pregnancy. Your baby's skin is protected by a whitish coating called vernix, and kicking, turning and possibly thumb-sucking are all part of the day. Many people have their anatomy scan around now.

This page covers 20 weeks 0 days to 20 weeks 6 days (20+0 to 20+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 20.

Botanical illustration of a grapefruit

About the size of a grapefruit

Typical estimated weight 330 g (12 oz) at 20+0, about 390 g (14 oz) by 20+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

  • A whitish, protective coating called vernix covers your baby's skin. It also helps during birth.2,3
  • Your baby is kicking, turning and may be sucking their thumb.2
  • Nails are growing toward the fingertips, and the areas of the brain that handle the five senses are developing.3
  • Your baby can hear and is becoming more active over these weeks.4
  • From about now, babies are measured from head to heel rather than head to bottom, because the legs are no longer tightly curled.2

Changes you may notice

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

  • Many people feel movement by now, often as bubbling or fluttering, but in a first pregnancy it can come a little later. Tell your midwife if you haven't felt any movement by 24 weeks.2,3,5
  • Calf cramps, often at night, are common. Rubbing the muscle firmly or pulling your toes up toward your ankle may help, and being more active during the day may reduce them.2
  • Tiredness, stretch marks, bleeding gums, heartburn, dizziness and swelling are all possible. Seek medical advice for any vaginal bleeding.2

Care around this week

  • In the US, the anatomy ultrasound is usually done between 18 and 22 weeks. UK: the 20-week screening scan is usually done between 18 and 21 weeks, sometimes up to 23 weeks. The sonographer checks your baby's growth and development and looks at the placenta; it usually takes around 30 minutes.2,6,7
  • UK: the whooping cough vaccine is usually offered around 20 weeks, and can be given from 16 weeks, ideally before 32. Protection passes through the placenta to help protect your baby until their own vaccines at 8 weeks old. In the US, Tdap is recommended during weeks 27 through 36.2,8,9
  • If your baby's movements slow down, change or stop, contact your midwife or maternity unit straight away. Don't wait until the next day or your next appointment.5
  • UK: your midwife or doctor can give you a MAT B1 maternity certificate from 20 weeks. You need it to claim maternity pay and benefits.2

Questions to ask your provider

  • Is there anything from my anatomy scan that needs follow-up?
  • Where is my placenta, and does its position matter for me?
  • When should I have the whooping cough (Tdap) vaccine?
  • What can I do about leg cramps at night?
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.11,12,13,14

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.13,15
  • 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.13,14,16,17
  • 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.5,13
  • 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.11,13,14
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.11,13,14
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.11,13,18
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.17,18
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.13,14,17
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.13,14
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.19
  • 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.13,20
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.13,21

Questions about 20 weeks

Is 20 weeks halfway through pregnancy?

Yes. A due date is set 280 days, or 40 weeks, from the first day of your last period, so 20 weeks is the halfway mark.2,10

What happens at the 20-week scan?

A sonographer checks your baby's growth and development and looks at the placenta. In England the scan looks for 11 conditions. It usually takes around 30 minutes and cannot find every condition.2,7

When do I have to tell my employer I'm pregnant in the UK?

The latest is 15 weeks before your due date, which is around week 25. Telling them gives you maternity rights and paid time off for antenatal appointments.2

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. 20 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. Ultrasound ExamsAmerican College of Obstetricians and Gynecologists
  7. 20-week screening scanNHS (England)
  8. Vaccinations in pregnancyNHS (England)
  9. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  10. Committee Opinion No. 700: Methods for Estimating the Due DateAmerican College of Obstetricians and Gynecologists, with AIUM and SMFM, 2017
  11. Pre-eclampsiaNHS (England)
  12. Epilepsy and pregnancyNHS (England)
  13. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  14. Pregnancy symptoms you need to get help forNHS (England)
  15. Vaginal bleeding in pregnancyNHS (England)
  16. Signs of going into labourNHS Best Start in Life
  17. Premature labour and birthNHS (England)
  18. Stomach pain in pregnancyNHS (England)
  19. Itching in pregnancyNHS (England)
  20. Severe vomiting in pregnancyNHS (England)
  21. 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