Baby's development, week-by-week
1st Trimester Changes
Your first trimester begins at conception and lasts until the end of the first 13 weeks of pregnancy. Right around the time you miss your period, you may start to notice the first signs of pregnancy, which are caused by changing hormone levels.
Note to partner/support person: The baby will grow from the size of a poppy seed to the size of a plum.
During this period it is important that you find balance in being supportive, helpful, and happy. This can be hard, as the first trimester is a new experience and they may not be showing much yet, nor can you feel the baby move. But by showing them your support in any way you can, you are already making this an easier experience.
Changes you may notice:
Weeks 4-7
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The placenta, amniotic sac, and umbilical cord start to form
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The neural tube begins to form (this will become your baby’s brain and spinal cord)
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Your baby’s heart has started beating (but you won’t be able to hear it at your appointments until 10 weeks or later)
Weeks 8-10
- Your baby’s arms and legs bud out like paddles from their curled body
- Webbed fingers and toes appear with soft nails on them, and their thin layer of skin is translucent
- Your baby’s nose, mouth, and ears are forming
Weeks 11-13
- Your baby has eyelids, but they are sealed shut
- Your baby has teeth buds that will grow into baby teeth
- Your baby will make their first movements, but they are too small for you to feel them yet
2nd Trimester Changes
Your second trimester takes you from Week 14 through Week 27. Your pregnancy is now well-established. Your nausea may have gone away, and you’re probably sleeping better, too. Overall, you might be feeling happy and content about your pregnancy.
Note to your partner/support person: The baby will grow from the side of a plum to a squash.
Changes you may notice:
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Increased hunger and energy
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Feeling the baby move inside you (this can feel like butterflies or gas bubbles)
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Your belly begins to show
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You may start wearing maternity clothes and larger-sized bras
Weeks 14-17
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Your baby’s skin is covered in soft hair (called lanugo)
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Your baby starts to gain weight more quickly
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Your baby’s genitals appear around Week 16
Weeks 18-21
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Your baby becomes more active, can flip over, and kicks more strongly
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Your baby might hiccup, swallow, and suck their thumb
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Your baby may be able to hear, and their other senses are developing
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Your baby’s skin begins to form a protective coating that will look like cream cheese at birth (called vernix)
Weeks 22-27
- Your baby wakes and sleeps (they might even smile in their sleep)
- Your baby can open their eyes, although they keep them closed most of the time
- Your baby might recognize familiar voices
3rd Trimester Changes
Your third trimester takes you from Week 28 through Week 40. Your body is changing to prepare for birth and breastfeeding. You might feel excited and nervous about the upcoming birth and parenthood.
Note to your partner/support person: The baby will grow from the size of a squash to a small watermelon.
Changes you may notice:
- Feeling a shortness of breath
- Your stomach may feel crowded (try eating smaller meals)
- Swelling of ankles
- Leaking colostrum (your early milk) from breasts
- Feeling warm-up contractions
Weeks 28-32
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Your baby’s brain develops more rapidly and grows larger
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The hair on your baby’s head may grow and thicken (and their body hair starts to disappear)
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Your baby gains more layers of fat, which help them control body temperature
Weeks 33-36
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Your baby’s lungs are more developed and getting ready to breathe on their own
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Your baby has grown to about 50 cm and will not grow longer before birth
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Their skull is made up of separate bones that will slide together as they go through the birth canal
Weeks 37-40
- Your baby has probably turned head-down and rests lower in your belly
- More fat is accumulating around your baby’s elbows, knees, and shoulders
- Your baby is gaining about a 110 to 225 grams per week in these last few weeks of pregnancy
Changes to your Body
How will my body change during pregnancy?
Breasts - The breasts become larger during pregnancy as the milk ducts begin growing rapidly.
Lungs - The lungs are compressed by the growing uterus later in pregnancy. Breathing deeply may become difficult.
Liver - The liver becomes more crowded, try to sleep on your left side can keep the pressure of the uterus off of it.
Stomach - The stomach becomes compressed later in pregnancy, making it difficult to eat large meals.
Bladder - The bladder is compressed by the baby's head and uterus later in pregnancy, causing the need to urinate more frequently.
Uterus - The uterus quadruples in size during pregnancy, and the stretching of the ligaments that hold it in place can cause discomfort.
Vagina - The vagina becomes softer and more expandable as labour approaches, and the pressure of the baby's head makes it look shorter.
Placenta - The placenta, which is an organ unique to pregnancy, attaches to the wall of the uterus.
Umbilical Cord - The umbilical cord acts as a road between mother and baby. It brings nutrients to the baby and pulls waste away.
