Pregnancy, week by week

Illustration of a baby at week 12 inside the womb in cross-section, with the placenta and umbilical cord
Womb in cross-section, enlarged to show detail. Not true size.

First trimester, week 12

12 weeks pregnant: Reflexes and the 12-week scan

Size of a
Lime
Length
5.4 cm crown to rump
Weight
14 g approximate
Heart rate
140–170 bpm typical range
Due date
196 days away 30% of the way
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All 40 weeks: real average sizes, what’s developing, what’s changing in your body, which scans are due, and the myths people search for, checked against published studies.

Find your week

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Every week at a glance

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

Scans & tests on one timeline

Full timeline

Can also show the baby’s sex

Myth or fact?

All 34 myths
Partly true

Is the nub theory accurate at 12 or 13 weeks?

It can be fairly accurate at 12–13 weeks in experienced hands, but it is an educated guess, not a diagnosis.

 Myth

Does a heart rate over 140 mean it’s a girl?

No. Studies comparing early heart rates in boys and girls found no meaningful difference. Heart rate depends mostly on gestational age.

 Myth

Does carrying high mean a girl and carrying low mean a boy?

No. The shape and height of a bump depend on your muscles, body shape, how many pregnancies you’ve had and the baby’s position, not the baby’s sex.

 Partly true

Does bad morning sickness mean you’re having a girl?

There’s a small statistical link between severe sickness and girls, but it can’t predict the sex of any one baby.

 Myth

Do babies move less at the end of pregnancy?

No. Movements may feel different as space gets tight, but the baby should keep moving as much as before, right up to and during labour.

 Myth

Do you need to eat for two when pregnant?

No. The NHS says there’s no need to “eat for 2”. US guidance suggests no extra calories in the first trimester, about 340 extra a day in the second, and about 450 in the third.

Common questions

How are pregnancy weeks counted?

From the first day of your last menstrual period (LMP), not from conception. That’s why you’re considered 2 weeks pregnant around the time you conceive, and why a full-term pregnancy is about 40 weeks.

When can you find out the baby’s gender?

The earliest reliable option is the NIPT blood test from 10 weeks. Ultrasound guesses using the nub theory are possible at 12–13 weeks, and the 18–22 week anatomy scan usually shows the sex clearly if the baby’s position allows.

When is the baby the size of a lime, lemon or banana?

Roughly a lime at 12 weeks (5.4 cm), a lemon at 13 weeks (7.4 cm), and the length of a banana at 20 weeks (about 25.6 cm from head to heel).

When do you feel the baby move?

Movements are usually first felt between 16 and 24 weeks. In a first pregnancy, you may not notice them until after 20 weeks.