Illustration of a baby at week 39 inside the womb in cross-section, with the placenta and umbilical cord
Womb in cross-section, enlarged to show detail. Not true size. Most babies are head-down by about 36 weeks.

Third trimester, week 39

39 weeks pregnant: Full term

Size of a
Mini watermelon
Length
50.7 cm head to heel
Weight
3.4 kg WHO median
Heart rate
110–160 bpm typical range
Due date
7 days away 98% of the way
12345678910111213141516171819202122232425262728293031323334353637383940

Checked against the sources listed on this page. Not reviewed by a clinician. Last updated 5 November 2026. How we check.

At 39 weeks pregnant, your baby is about the size of a mini watermelon: roughly 50.7 cm from head to heel, weighing about 3.4 kg. You’re in your third trimester, with about 1 week to go until your due date.

Your baby this week

  • The baby is full term. Body fat makes up about 15% of their weight, which keeps them warm.
  • The skull bones can overlap slightly to fit through the birth canal.
  • The brain is still growing fast. It will roughly double in size in the first year.

Your body this week

  • You may feel pelvic pressure, backache or an urge to nest.
  • A membrane sweep may be offered around 39–41 weeks to encourage labour to start.
  • Only about 4% of babies arrive on their exact due date.
Typical weight gain so far
11.2–15.5 kg
Your uterus
Near the ribs, may drop as baby engages

Weight gain range is for a pre-pregnancy BMI of 18.5–24.9 (IOM guideline). Your provider may advise differently.

Scans, tests and checkups

  • This week
    Know your baby’s movements Self-care

    Get to know your baby’s pattern. If movements slow down, change or stop, contact your maternity unit straight away. Don’t wait until the next day.

  • This week
    Weekly checkups Checkup

    Blood pressure, urine, growth, position and movements, plus planning for labour. Often weekly in the US. The NHS schedule is usually 36, 38 and 40 weeks.

  • This week
    Membrane sweep & post-dates plan Checkup

    A membrane sweep may be offered. If labour doesn’t start, induction is usually offered between 41 and 42 weeks.

See the full scan and test timeline

Real size, next to an adult hand

Adult hand 18.5 cmbaby 34.5 cm curled up

Growth curve

01 kg2 kg3 kgwk 10wk 20wk 30wk 40
Typical weight by week: WHO median from week 20, approximate before that. Healthy babies vary widely.

When to call your midwife or doctor at 39 weeks

Call your midwife, doctor or maternity unit straight away, day or night, if you have any of these:

  • A change in your baby’s usual pattern of movement. Call straight away rather than waiting until the next day.
  • Vaginal bleeding, or a gush or steady trickle of fluid.
  • Severe belly pain that doesn’t go away.
  • A severe headache, vision changes, pain under your ribs, or sudden swelling of your face, hands or feet. These can be signs of pre-eclampsia.
  • Regular, strong contractions or your waters breaking. Follow what your maternity team told you about when to come in.
  • Intense itching, especially on your hands and feet, which can be a sign of a liver condition called cholestasis.
  • Fever of 38 °C (100.4 °F) or higher, or pain or burning when you pee.
  • Pain or swelling in one leg, chest pain, or sudden shortness of breath. These can be signs of a blood clot.
  • Feeling very low, hopeless or anxious most days. If you feel you might harm yourself, get emergency help.

Based on NHS and ACOG guidance. This list isn’t complete. If something feels wrong, call anyway. In an emergency, call your local emergency number.

Tip for this week

Prepare a quiet “labour nest” at home: pillows, a birthing ball, water, snacks and a playlist.

Myth or fact?

Will my baby be born on the due date?

Myth

Unlikely. Only about 4% of babies arrive on their exact due date. Most are born within about two weeks either side.

Read the evidence

Common questions at this stage

All common questions

More myths around week 39

Questions people ask about week 39

Is 39 weeks full term?

Yes. Full term is 39 weeks 0 days to 40 weeks 6 days.

What is a membrane sweep?

During an internal exam, a midwife or doctor sweeps a finger around the cervix to separate the membranes, which releases hormones that may start labour. It can be uncomfortable but is safe.

References

  1. NHS Best Start in Life: 39 weeks pregnant
  2. NHS: Your antenatal appointments
  3. NHS: Your baby’s movements
  4. NHS: Pre-eclampsia
  5. Kiserud T et al. The WHO Fetal Growth Charts. PLoS Medicine, 2017
  6. NHS: Itching and intrahepatic cholestasis of pregnancy
  7. NHS: Signs that labour has begun
  8. MedlinePlus (US National Library of Medicine): Fetal development

Advice differs between countries, so follow your own care team’s plan. Weights from week 20 are the WHO median, and earlier weights are approximate. How we check this.

All 40 weeks

First trimester Weeks 1–13

From conception to a fully formed, tiny fetus. The most rapid change of the whole pregnancy.

  1. Prenatal development at week 1 Week 1A new cycle begins
  2. Prenatal development at week 2 Week 2Ovulation — and maybe conception
  3. Prenatal development at week 3 Week 3A ball of cells finds its home
  4. Prenatal development at week 4 Week 4Poppy seed
  5. Prenatal development at week 5 Week 5Sesame seed
  6. Prenatal development at week 6 Week 6Lentil
  7. Prenatal development at week 7 Week 7Blueberry
  8. Prenatal development at week 8 Week 8Raspberry
  9. Prenatal development at week 9 Week 9Cherry
  10. Prenatal development at week 10 Week 10Strawberry
  11. Prenatal development at week 11 Week 11Fig
  12. Prenatal development at week 12 Week 12Lime
  13. Prenatal development at week 13 Week 13Lemon

Second trimester Weeks 14–27

Growth, movement and senses. Often the most comfortable stretch for parents.

  1. Prenatal development at week 14 Week 14Peach
  2. Prenatal development at week 15 Week 15Apple
  3. Prenatal development at week 16 Week 16Avocado
  4. Prenatal development at week 17 Week 17Pear
  5. Prenatal development at week 18 Week 18Bell pepper
  6. Prenatal development at week 19 Week 19Mango
  7. Prenatal development at week 20 Week 20Banana
  8. Prenatal development at week 21 Week 21Carrot
  9. Prenatal development at week 22 Week 22Papaya
  10. Prenatal development at week 23 Week 23Grapefruit
  11. Prenatal development at week 24 Week 24Ear of corn
  12. Prenatal development at week 25 Week 25Cauliflower
  13. Prenatal development at week 26 Week 26Zucchini
  14. Prenatal development at week 27 Week 27Head of lettuce

Third trimester Weeks 28–40

Weight gain, brain and lung maturation, and getting into position for birth.

  1. Prenatal development at week 28 Week 28Eggplant
  2. Prenatal development at week 29 Week 29Butternut squash
  3. Prenatal development at week 30 Week 30Cabbage
  4. Prenatal development at week 31 Week 31Coconut
  5. Prenatal development at week 32 Week 32Napa cabbage
  6. Prenatal development at week 33 Week 33Pineapple
  7. Prenatal development at week 34 Week 34Cantaloupe
  8. Prenatal development at week 35 Week 35Honeydew melon
  9. Prenatal development at week 36 Week 36Papaya (large)
  10. Prenatal development at week 37 Week 37Winter melon
  11. Prenatal development at week 38 Week 38Pumpkin (small)
  12. Prenatal development at week 39 Week 39Mini watermelon
  13. Prenatal development at week 40 Week 40Watermelon