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Third trimester

28 weeks pregnant

At 28 weeks 0 days the third trimester begins. Your baby is gaining fat, the brain is growing quickly and the lungs are still maturing. Several care topics often come up now, including Rh immune globulin if you are Rh negative, vaccines and the results of glucose screening.

This page covers 28 weeks 0 days to 28 weeks 6 days (28+0 to 28+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 28.

Botanical illustration of a pineapple

About the size of a pineapple

Typical estimated weight 1.21 kg (2 lb 11 oz) at 28+0, about 1.35 kg (3 lb 0 oz) by 28+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's heart rate is now around 140 beats per minute, much faster than an adult's. It is high partly because a small heart pumps less blood with each beat, and the fast rate also helps keep your baby warm.2
  • The brain is growing rapidly, and the eyelids can open and close.3
  • The lungs are producing surfactant, which helps the air sacs fill with air after birth, but they are still immature.3,4
  • Your baby continues to build up fat reserves, and some babies begin turning head-down around this time as they get ready for birth.4

Changes you may notice

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

  • Heartburn and indigestion are common now, caused by hormones and the growing baby. Your back may ache as joints and ligaments loosen and carry extra weight.2
  • Swelling in the ankles, feet and face is common, especially in hot weather. Have it checked by your midwife or doctor, as it can sometimes be a sign of pre-eclampsia, which raises blood pressure.2
  • Nosebleeds are common in pregnancy because of hormone changes. Sitting upright, leaning forward and pinching just above the nostrils for 10 to 15 minutes may help.2
  • Over the coming weeks you may feel more uncomfortable and tired. Rest helps many symptoms; contact your midwife or doctor if anything worries you.2

Care around this week

  • If your blood type is Rh negative, Rh immune globulin is usually given around 28 weeks in the US. In the UK, if you are RhD negative and your baby is RhD positive, you'll be offered an anti-D injection to stop you developing antibodies.5,6
  • In the US, Tdap is recommended during weeks 27 through 36, preferably early in that window, and the maternal RSV vaccine is given at 32 to 36 weeks, from September to January in most areas. In the UK, the RSV vaccine is offered around the 28-week appointment and is best given as soon as possible from 28 weeks.7,8,9
  • Gestational diabetes screening is usually done between 24 and 28 weeks, so results or follow-up may be discussed now. In the UK, a routine antenatal appointment is offered at 28 weeks.10,11
  • Keep noticing your baby's usual pattern of movements. If movements slow down, stop or change, contact your midwife, provider or maternity unit straight away, even in the middle of the night. Don't use a home Doppler to check on your baby.12

Questions to ask your provider

  • Do I need Rh immune globulin, and can I have it at this visit?
  • Which vaccines do you recommend for me now, and when?
  • What were my glucose screening results, and is any follow-up needed?
  • How often will my visits be during the third trimester?
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.15,16,17,18

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.17,19
  • 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.17,18,20,21
  • 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.12,17
  • 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.15,17,18
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.15,17,18
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.15,17,22
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.21,22
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.17,18,21
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.17,18
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.23
  • 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.17,24
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.17,25

Questions about 28 weeks

When does the third trimester start?

The third trimester starts at 28 weeks 0 days and continues until birth. The second trimester runs from 14 weeks 0 days to 27 weeks 6 days.13

How many times should my baby move at 28 weeks?

There is no set number of movements, and you don't need to count kicks. What matters is your baby's usual pattern. If movements slow down or change, contact your midwife, provider or maternity unit straight away.12

Is it safe to sleep on my back at 28 weeks?

Going to sleep on your side is recommended from now on. 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.14

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. 28 weeks pregnant guideNHS Best Start in Life
  3. Fetal developmentUS National Library of Medicine
  4. Fetal development: stages of growthCleveland Clinic
  5. Practice Bulletin No. 181: Prevention of Rh D AlloimmunizationAmerican College of Obstetricians and Gynecologists, 2017
  6. Haemolytic disease of the fetus and newborn (HDFN)NHS (England)
  7. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  8. Protecting Infants from RSVUS Centers for Disease Control and Prevention
  9. Vaccinations in pregnancyNHS (England)
  10. Practice Bulletin No. 190: Gestational Diabetes MellitusAmerican College of Obstetricians and Gynecologists, 2018
  11. Your antenatal appointmentsNHS (England)
  12. Your baby's movementsNHS (England)
  13. How Your Fetus Grows During PregnancyAmerican College of Obstetricians and Gynecologists
  14. 27 weeks pregnant guideNHS Best Start in Life
  15. Pre-eclampsiaNHS (England)
  16. Epilepsy and pregnancyNHS (England)
  17. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  18. Pregnancy symptoms you need to get help forNHS (England)
  19. Vaginal bleeding in pregnancyNHS (England)
  20. Signs of going into labourNHS Best Start in Life
  21. Premature labour and birthNHS (England)
  22. Stomach pain in pregnancyNHS (England)
  23. Itching in pregnancyNHS (England)
  24. Severe vomiting in pregnancyNHS (England)
  25. 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