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Pregnancy week by week

What is developing, what you may notice and what to ask about, for every week from 1 to 42. Each page uses completed weeks, cites its sources and shows a typical size from published growth equations.

Sources last checked . How we write and check

First0 to 13+6
Second14+0 to 27+6
Third28+0 to birth
Weeks of pregnancy counted from the first day of the last period, using ACOG trimester boundaries. The apricot band marks early, full and late term (37+0 to 41+6).

Weeks count from the first day of the last period, so conception is around week 2 and weeks 1 and 2 come before pregnancy begins.1 “Week 12” on this site means 12 weeks 0 days to 12 weeks 6 days. Not sure which week you’re in? Find out how far along you are.

First trimester

Weeks 1–13. About the first trimester

  1. 1 week pregnantAt 1 week, you are not pregnant yet.
  2. 2 weeks pregnantAt 2 weeks, you are still not pregnant, because pregnancy is counted from the first day of your last period.
  3. 3 weeks pregnantAt 3 weeks, conception may have happened: a sperm and egg join in a fallopian tube.
  4. 4 weeks pregnantSize of a poppy seedAt 4 weeks, the blastocyst is settling into the lining of your womb, and the structures that will become the placenta and amniotic sac are forming.
  5. 5 weeks pregnantSize of a sesame seedAt 5 weeks, the embryonic period is getting underway, when the baby's major organs and body systems begin to form.
  6. 6 weeks pregnantSize of a lentilAt 6 weeks, the embryo is changing fast.
  7. 7 weeks pregnantSize of a blueberryAt 7 weeks, the embryo is growing very quickly.
  8. 8 weeks pregnantSize of a raspberryAt 8 weeks, the embryo is growing quickly: the arms and legs are getting longer, hands and feet are forming, and the placenta is developing.
  9. 9 weeks pregnantSize of a green oliveAt 9 weeks, the face is becoming more recognizable, with eyelids, a mouth and a tongue, and fingers and toes are starting to take shape.
  10. 10 weeks pregnantSize of a strawberryAt 10 weeks, the face is becoming more distinct, the outer ears are forming and the fingers and toes are no longer webbed.
  11. 11 weeks pregnantSize of a figAt 11 weeks, fingers and toes are separating, tiny nails are appearing and the fetus can open and close its hands.
  12. 12 weeks pregnantSize of a limeAt 12 weeks, the organs, limbs, bones and muscles are all present and keep maturing.
  13. 13 weeks pregnantSize of a lemonAt 13 weeks, you are in the final week of the first trimester, which ends at 13 weeks 6 days.

Second trimester

Weeks 14–27. About the second trimester

  1. 14 weeks pregnantSize of a nectarineAt 14 weeks 0 days, the second trimester begins.
  2. 15 weeks pregnantSize of an appleAt 15 weeks you are in the second trimester, which runs from 14 weeks to just before 28 weeks.
  3. 16 weeks pregnantSize of an avocadoAt 16 weeks your baby's developing nervous system lets them move their arms and legs and make fists, and hearing keeps developing.
  4. 17 weeks pregnantSize of a pomegranateAt 17 weeks your baby can move their eyes behind closed lids, open and close their mouth, and react to loud noises.
  5. 18 weeks pregnantSize of a bell pepperAt 18 weeks your baby's hearing, swallowing and sucking reflexes are developing, and there is plenty of wriggling.
  6. 19 weeks pregnantSize of a mangoAt 19 weeks your baby is becoming more active, and hearing is developing.
  7. 20 weeks pregnantSize of a grapefruitAt 20 weeks you are halfway through a 40-week pregnancy.
  8. 21 weeks pregnantSize of an eggplantAt 21 weeks you are in the second half of pregnancy.
  9. 22 weeks pregnantSize of a papayaAt 22 weeks you are well into the second trimester.
  10. 23 weeks pregnantSize of an acorn squashAt 23 weeks your baby's limbs are now in proportion and the body is starting to store fat.
  11. 24 weeks pregnantSize of a coconutAt 24 weeks your baby's body is in proportion, the lungs are still maturing, and fat is being laid down.
  12. 25 weeks pregnantSize of a cauliflowerAt 25 weeks your baby is active, filling out with fat, and may react to loud sounds.
  13. 26 weeks pregnantSize of a red cabbageAt 26 weeks you are nearing the end of the second trimester.
  14. 27 weeks pregnantSize of a cantaloupeAt 27 weeks you are in the final week of the second trimester.

Third trimester

Weeks 28–42. About the third trimester

  1. 28 weeks pregnantSize of a pineappleAt 28 weeks 0 days the third trimester begins.
  2. 29 weeks pregnantSize of a butternut squashAt 29 weeks you are in the third trimester, which ACOG counts from 28 weeks.
  3. 30 weeks pregnantSize of a kabocha squashAt 30 weeks you are about three-quarters of the way through pregnancy.
  4. 31 weeks pregnantSize of a napa cabbageAt 31 weeks your baby is growing quickly and adding fat, and makes rhythmic breathing movements even though the lungs are not fully mature.
  5. 32 weeks pregnantSize of a spaghetti squashAt 32 weeks your baby is fully formed and mainly needs to gain weight, while the lungs and brain keep maturing.
  6. 33 weeks pregnantSize of a durianAt 33 weeks your baby's bones are hardening, though the skull bones stay soft to help with birth.
  7. 34 weeks pregnantSize of a honeydew melonAt 34 weeks your baby is curled up with legs tucked toward the chest, and space in the uterus is tight.
  8. 35 weeks pregnantSize of a Crenshaw melonAt 35 weeks your baby keeps gaining weight and fat, which will help with temperature control after birth, and the brain is still growing.
  9. 36 weeks pregnantSize of a sugar pumpkinAt 36 weeks 0 days to 36 weeks 6 days, your baby is still putting on fat and their lungs are probably close to ready for breathing outside the womb.
  10. 37 weeks pregnantSize of a Hubbard squashFrom 37 weeks 0 days to 38 weeks 6 days, ACOG calls a pregnancy early term.
  11. 38 weeks pregnantSize of a jackfruitAt 38 weeks 0 days to 38 weeks 6 days, you are still early term by ACOG's definition, and full term begins at 39 weeks 0 days.
  12. 39 weeks pregnantSize of a winter melonAt 39 weeks 0 days to 39 weeks 6 days, your pregnancy has reached full term, which ACOG defines as 39 weeks 0 days to 40 weeks 6 days.
  13. 40 weeks pregnantSize of a small watermelonAt 40 weeks 0 days to 40 weeks 6 days, you are still full term, which ACOG defines as 39 weeks 0 days to 40 weeks 6 days.
  14. 41 weeks pregnantAt 41 weeks 0 days to 41 weeks 6 days, your pregnancy is late term by ACOG's definition.
  15. 42 weeks pregnantFrom 42 weeks 0 days, ACOG calls a pregnancy postterm.

How these pages are written

Development and symptom notes summarize public guidance from the NHS, MedlinePlus, Cleveland Clinic and ACOG, cited line by line on each page. Typical sizes are computed, not copied: crown-rump length for weeks 7 to 13 from the Robinson equation, and estimated weight for weeks 14 to 40 from Hadlock’s growth standard.2,3 The fruit and vegetables are a rough visual guide. Read our methods and editorial policy.

Sources

  1. How Your Fetus Grows During PregnancyAmerican College of Obstetricians and Gynecologists
  2. A critical evaluation of sonar “crown-rump length” measurementsBritish Journal of Obstetrics and Gynaecology 82(9):702–710, 1975
  3. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991

Links checked November 12, 2026. Citing a source does not mean it endorses this site.