Free family guide · Pregnancy week by week · Second trimester

27 weeks pregnant

Week 27 is in the second trimester in both the US Office on Women's Health (OWH) system and the UK's NHS week-by-week guide.[1][2]

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Sources on this page: OWH; NHS; ACOG; USPSTF; NICHD; CDC; NIMH; HRSA; MedlinePlus

This page shares what health organizations say. It is not medical advice. It is general information. Talk to your doctor, midwife or pediatrician about your own situation.

In an emergency, call 911.

At a glance

  • The NHS says the baby is around 36.6 cm long.[3]
  • The NHS says the lungs are now capable of breathing, and the baby is filling out with fat.[3]
  • The NHS says sleeping on either side is better than on your back.[3]

Which trimester is week 27?

OWH counts the trimesters as weeks 1 to 12, 13 to 28 and 29 to 40.[1] The NHS guide counts them as weeks 4 to 12, 13 to 27 and 28 to 41.[2] ACOG counts the first trimester to 13 weeks 6 days, the second from 14 weeks to 27 weeks 6 days, and the third from 28 weeks to 40 weeks 6 days.[4]

All three place week 27 in the second trimester.[1][2][4]

Your body this week

The NHS says snoring is common now.[3]

Your baby this week

The NHS says the baby is around 36.6 cm long.[3]

The NHS says the lungs are now capable of breathing, and the baby is filling out with fat.[3]

Visits and tests around week 27

Sources differ

Sources give different weeks for the gestational diabetes test:[5][6][7][8]

  • The US Preventive Services Task Force advises screening at 24 weeks or later.[5]
  • NICHD says screening usually happens between 24 and 28 weeks.[6]
  • ACOG says glucose screening is usually done between 24 and 28 weeks, with blood drawn an hour after a sugar drink.[7]
  • OWH lists glucose challenge and tolerance tests at weeks 26 to 28.[8]

OWH lists a nonstress test after week 28, when a provider orders one.[8]

For a healthy pregnancy, NICHD describes visits once a month until 28 weeks.[6]

Things to do this week

  • The NHS says sleeping on either side is better than on your back.[3]
  • The NHS says research suggests that after week 28, going to sleep on your back can double the risk of stillbirth.[3]
  • The NHS suggests a pillow under your belly and between the legs, and rolling back onto your side if you wake on your back.[3]
  • CDC says to avoid lying flat on your back during exercise after the first trimester.[9]

Feelings check-in

The National Institute of Mental Health (NIMH) says perinatal depression includes depression during pregnancy, and its signs last at least 2 weeks.[10]

HRSA says the National Maternal Mental Health Hotline, 1-833-852-6262, takes calls and texts 24/7 in English and Spanish.[11]

When to call your provider or get help

MedlinePlus says gestational high blood pressure and preeclampsia start after 20 weeks, and high blood pressure is often found only at checkups.[12]

CDC lists urgent warning signs to watch for during pregnancy and in the year after birth, including:[13]

  • a headache that will not go away or gets worse;[13]
  • changes in vision;[13]
  • extreme swelling of the hands or face;[13]
  • severe belly pain that does not go away;[13]
  • the baby's movement stopping or slowing;[13]
  • vaginal bleeding or leaking fluid;[13]
  • thoughts of harming yourself or the baby.[13]

Questions families ask

Which trimester is week 27?

OWH places week 27 in the second trimester.[1] The NHS guide places it in the second trimester.[2] ACOG places it in the second trimester.[4]

How big is the baby at 27 weeks?

The NHS says the baby is around 36.6 cm long.[3]

What is the safest sleep position in late pregnancy?

The NHS says the safest position to go to sleep is on your side, left or right.[14] It says research suggests that after 28 weeks, falling asleep on your back can double the risk of stillbirth.[14]

Free from UpOnly Learning. Written for families of every faith. No outside ads and no affiliate links. Every fact on this page comes from the sources listed below. How we source and review these pages

Updated 2026-10-24: first published.

Sources

All sources were opened and checked on the date shown.

  1. Office on Women's Health (HHS). Stages of pregnancy. Checked October 24, 2026.
  2. NHS (United Kingdom). Week-by-week guide to pregnancy. Checked October 24, 2026.
  3. NHS (United Kingdom). 27 weeks pregnant guide. Checked October 24, 2026.
  4. American College of Obstetricians and Gynecologists. How Your Fetus Grows During Pregnancy. Checked October 24, 2026.
  5. US Preventive Services Task Force. Gestational Diabetes: Screening. Checked October 24, 2026.
  6. Eunice Kennedy Shriver National Institute of Child Health and Human Development (NIH). What happens during prenatal visits?. Checked October 24, 2026.
  7. American College of Obstetricians and Gynecologists. Routine Tests During Pregnancy. Checked October 24, 2026.
  8. Office on Women's Health (HHS). Prenatal care and tests. Checked October 24, 2026.
  9. Centers for Disease Control and Prevention. Pregnant & Postpartum Activity: An Overview. Checked October 24, 2026.
  10. National Institute of Mental Health (NIH). Perinatal Depression. Checked October 24, 2026.
  11. Health Resources and Services Administration (HRSA). National Maternal Mental Health Hotline. Checked October 24, 2026.
  12. MedlinePlus (National Library of Medicine). High Blood Pressure in Pregnancy. Checked October 24, 2026.
  13. Centers for Disease Control and Prevention (HEAR HER campaign). Urgent Maternal Warning Signs and Symptoms. Checked October 24, 2026.
  14. NHS (United Kingdom). Tiredness and sleep problems in pregnancy. Checked October 24, 2026.