Trimesters

Pregnancy trimesters mean that your pregnancy is divided into three phases: the first trimester, second trimester, and third trimester. Each trimester is 13 or 14 weeks long to equal 40 weeks of pregnancy. The first trimester lasts until you're 13 weeks pregnant, the second trimester spans week 14 to week 27, and the third trimester starts the day you turn 28 weeks pregnant and lasts until week 40 – though you're likely to deliver your baby a few weeks before or after that.

First Trimester

animation of fetus
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Inside pregnancy: Weeks 10 to 14
Reviewed by Layan Alrahmani, M.D., ob-gyn, MFM
Blastocyst moving to the uterus
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Your pregnancy: Week 4
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
An egg being swept up in the fallopian tube
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Your pregnancy: Week 2
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 6 week old embryo in the uterus
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Your pregnancy: Week 6
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Close-up view of a 7 week old embryo in the uterus
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Your pregnancy: Week 7
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
tabletop with plate of lemons, cup of hot water, and ginger root
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Checklist: First trimester
woman talking
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What the first trimester feels like
Side-view of an 10 week old fetus in the uterus, you can see the umbilical cord and the placenta
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Your pregnancy: Week 10
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Front view of an 11 week old fetus in the uterus, you can see the umbilical cord and the placenta
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Your pregnancy: Week 11
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Wide shot of a 12 week old fetus in the uterus, you can see the umbilican cord and the placenta
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Your pregnancy: Week 12
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Close-up of a 13 week old fetus in the uterus
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Your pregnancy: Week 13
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Morula floating through fallopian tube
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Your pregnancy: Week 3
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 5 week old embryo in the uterus
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Your pregnancy: Week 5
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Side-view of an 8 week old embryo in the uterus
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Your pregnancy: Week 8
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Front view of a 9 week old embryo in the uterus
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Your pregnancy: Week 9
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
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Second Trimester

A wide shot of your 15 week old baby in the uterus, you can see the placenta
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Your pregnancy: Week 15
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 19 week old baby in the uterus, the baby is holding it's umbilical cord
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Your pregnancy: Week 19
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 23 week old baby in the uterus, the baby's hand is touching its mouth, the rib cage is visible through the skin
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Your pregnancy: Week 23
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
cartoon images of water birth, pregnant woman on knees, and pregnant woman squatting with man supporting her
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Checklist: Second trimester
woman talking
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What the second trimester feels like
A medium shot of the face of your 14 week old baby in the uterus
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Your pregnancy: Week 14
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 16 week old baby, in the uterus, puts its thumb in its mouth
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Your pregnancy: Week 16
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 17 week old baby in the uterus
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Your pregnancy: Week 17
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of an 18 week old baby in the uterus, the nerves and spinal cord are visible through skin
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Your pregnancy: Week 18
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 20 week old baby in the uterus, the baby is holding it's umbilical cord
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Your pregnancy: Week 20
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 21 week old baby in the uterus
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Your pregnancy: Week 21
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 22 week old baby in the uterus, the baby's hand is touching its face
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Your pregnancy: Week 22
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 24 week old baby in the uterus
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Your pregnancy: Week 24
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 25 week old baby in the uterus, the baby has it's thumb in it's mouth, and the umbilical cord can be seen
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Your pregnancy: Week 25
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 26 week old baby in the uterus
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Your pregnancy: Week 26
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side-view of 27 week old baby in the uterus, the umbilical cord can be seen
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Your pregnancy: Week 27
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
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Third Trimester

woman holding card with text: active labor
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Checklist: Third trimester
A close-up of a 32 week old baby in the uterus, the baby's fingers are touching their mouth
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Your pregnancy: Week 32
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side-view close-up of a 35 week old baby in the uterus
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Your pregnancy: Week 35
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side-view close-up of a 36 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 36
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A wide-view of a 37 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 37
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A wide-view of a 39 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 39
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 28 week old baby in the uterus, the baby's eyes are open and their hand is in front of their mouth
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Your pregnancy: Week 28
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side-view of 29 week old baby in the uterus, the umbilical cord and placenta can be seen
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Your pregnancy: Week 29
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 30 week old baby in the uterus
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Your pregnancy: Week 30
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 31 week old baby in the uterus, the skull is transparent so the fontanellescan be seen
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Your pregnancy: Week 31
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 33 week old baby in the uterus
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Your pregnancy: Week 33
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 34 week old baby in the uterus, the baby's fingers are under their nose
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Your pregnancy: Week 34
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A wide-view of a 38 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 38
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A close-up of a 40 week old baby in the uterus
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Your pregnancy: Week 40
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side-view of a 41 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 41
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
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Latest in trimesters

A side-view of a 41 week old baby in the uterus, the placenta and umbilical cord can be seen
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Your pregnancy: Week 41
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 17 week old baby in the uterus
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Your pregnancy: Week 17
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A 16 week old baby, in the uterus, puts its thumb in its mouth
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Your pregnancy: Week 16
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of an 18 week old baby in the uterus, the nerves and spinal cord are visible through skin
go to video page
Your pregnancy: Week 18
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 19 week old baby in the uterus, the baby is holding it's umbilical cord
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Your pregnancy: Week 19
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
A side view of a 20 week old baby in the uterus, the baby is holding it's umbilical cord
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Your pregnancy: Week 20
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
An egg being swept up in the fallopian tube
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Your pregnancy: Week 2
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn
Morula floating through fallopian tube
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Your pregnancy: Week 3
Reviewed by Shannon Smith, M.D., FACOG, ob-gyn

Community

  • October 2024 Birth Club
    trimesters
    By londyn06
    how many weeks are considered 3rd trimester? im currently 27 and dont know if im in my 3rd trimester now or not til next week
    07-17-24 by Lilbutterfli94
    Number of comments2
    no reactions
    0
  • September 2025 Birth Club
    Trimester
    By HaleySD
    Is beginning of second trimester at 13 weeks or 14 weeks? Both of my pregnancy apps say something different
    02-26-25 by Roseingarden
    Number of comments2
    replied with hug
    1
  • Pregnancy
    Trimesters
    By nelizabeth93
    Im 27 weeks today. Am I in the third trimester now or still the second?
    09-01-23 by NikitaAdrian
    Number of comments2
    no reactions
    0
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