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Second trimester

27 weeks pregnant

At 27 weeks you are in the final week of the second trimester. Your baby is filling out with fat, the brain is growing rapidly, and the lungs are making surfactant but are still immature. In the US, the Tdap vaccine window opens this week.

This page covers 27 weeks 0 days to 27 weeks 6 days (27+0 to 27+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 27.

Botanical illustration of a cantaloupe

About the size of a cantaloupe

Typical estimated weight 1.06 kg (2 lb 5 oz) at 27+0, about 1.19 kg (2 lb 10 oz) by 27+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

  • Your baby is getting plumper as fat fills out the skin, and the organs continue to mature in preparation for life outside the womb.2,3
  • The brain grows rapidly from about 27 to 30 weeks.4
  • The lungs are producing surfactant, which helps the air sacs fill with air after birth, but they are still maturing.3,4
  • Your baby can open and close their eyes and has eyelashes.3,4

Changes you may notice

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

  • Bloating and constipation are common, partly because of the growing baby pressing on your stomach and partly because of the hormone progesterone. Drinking plenty of water and eating high-fiber foods, fruit and vegetables may help.2
  • Tiredness is common, so rest or nap when you can. Some people start snoring because the lining of the nose can swell in pregnancy.2
  • Other symptoms that may continue include backache, heartburn, leg cramps, swollen hands and feet, headaches and round ligament pain.2

Care around this week

  • In the US, the Tdap vaccine is recommended during weeks 27 through 36 of each pregnancy, preferably early in that window, to help protect your baby from whooping cough. In the UK, the whooping cough vaccine can be given from 16 weeks and ideally before 32 weeks; ask your midwife or GP if you haven't had it.5,6
  • Gestational diabetes screening is usually done between 24 and 28 weeks. If you are Rh negative, Rh immune globulin is usually given around 28 weeks, so it may come up at your next visit.7,8
  • If your baby's movements slow down, stop or change from their usual pattern, contact your midwife, provider or maternity unit straight away. Don't wait for the next day.9

Questions to ask your provider

  • Can I have the Tdap vaccine at this visit?
  • Do I need Rh immune globulin, and when would I get it?
  • When will I get the results of my gestational diabetes screening?
  • Do I need a letter to fly from here on?
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.9,13
  • 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 27 weeks

Is 27 weeks the third trimester?

Not quite. The second trimester runs through 27 weeks 6 days, and the third trimester starts at 28 weeks 0 days.10

When should I get the Tdap vaccine?

In the US, Tdap is recommended during weeks 27 through 36 of every pregnancy, preferably early in that window. In the UK, the whooping cough vaccine is usually offered around 20 weeks and can be given from 16 weeks, ideally before 32 weeks.5,6

Should I stop sleeping on my back?

Going to sleep on your side is recommended. After 28 weeks, research suggests sleeping on your back can double the risk of stillbirth. If you wake up on your back, just turn onto your side again.2

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. 27 weeks pregnant guideNHS Best Start in Life
  3. Fetal development: stages of growthCleveland Clinic
  4. Fetal developmentUS National Library of Medicine
  5. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  6. Vaccinations in pregnancyNHS (England)
  7. Practice Bulletin No. 190: Gestational Diabetes MellitusAmerican College of Obstetricians and Gynecologists, 2018
  8. Practice Bulletin No. 181: Prevention of Rh D AlloimmunizationAmerican College of Obstetricians and Gynecologists, 2017
  9. Your baby's movementsNHS (England)
  10. How Your Fetus Grows During PregnancyAmerican College of Obstetricians and Gynecologists
  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