Your developing baby: weeks 6–42 

Although there are big changes happening during the first few weeks of your pregnancy, most of them are happening inside your body. Your baby bump probably isn’t showing, so most people won’t be able to tell that you’re pregnant.

Your developing baby

6–7 weeks

At 7 weeks your baby is about 8 mm long from head to bottom. The brain is growing and the heart is beginning to beat. Ears, eyes, arms, and legs are also starting to grow. Your baby will start to move, but you won’t be able to feel it yet.

8–9 weeks

At 9 weeks your baby is about 17 mm long from head to bottom. Your baby’s face is slowly forming and there are eyelids. They have a mouth and a tongue. Hands and feet, with ridges where the fingers and toes will be, are also beginning to grow.

10–12 weeks

By 12 weeks your baby is fully formed. They have all their organs, muscles, limbs and bones and can kick and move.

13–14 weeks

By 14 weeks the baby can swallow and their fingerprints have formed.

14–16 weeks

Your baby can swallow, suck and grip and is covered in soft, downy hair. Baby’s arms and legs are working and moving. Second-time mothers may feel baby move (sometimes called ‘quickening’) at about 16 weeks.

17–20 weeks

Your baby is getting bigger and putting on weight. Their heart is beating – much faster than yours. They are moving and kicking. First-time mothers may feel baby move (sometimes called ‘quickening’) at about 20 weeks.

21–24 weeks

By 24 weeks your baby is about 30 cm long and weighs 600 g (or a little bit bigger than a pack of butter). Their skin is thicker and less see-through (transparent) than before but remains wrinkled because there is no fat underneath. Your baby can hear voices and is moving strongly. Your baby starts practicing breathing and swallowing movements.

25–27 weeks

Your baby can recognize your voice. The baby has a pattern of wake and sleep times. Their eyes begin to open. Baby starts sucking their fingers and thumbs.

28–30 weeks

At 28 weeks your baby is over 38 cm long and is about 900 g in weight (nearly 2 packs of butter!). Your baby’s skin begins to develop a white, greasy covering called vernix, which waterproofs the skin. Baby’s movements can easily be felt at this stage. By week 30 your baby is about 43 cm long and weighs about 1.3 kg.

30–32 weeks

Your baby’s eyes are open and baby can see and hear. Baby doesn’t grow much more but does gain weight. There’s less room for your baby to move around.

33–36 weeks

The baby may have a full head of hair. Your baby usually settles into a head-down position and moves down so that their head is in your pelvis. Your baby’s lungs are almost fully grown.

37–40 weeks

The baby keeps gaining weight. The downy hair and vernix coating are gone. Your baby may sit low in your pelvis.

By 40 weeks your baby is about 50 cm long and weighs over 3 kg – remember though that all babies are different; babies can be longer or shorter, bigger or smaller. Your baby is now fully developed and the lungs have matured, ready for birth.

41–42 weeks

Most babies are not born on their due dates. You may be waiting a little bit longer for the baby to arrive!

Your changing body

During early pregnancy you may have some or all of the following: 

  • no periods or lighter bleeding
  • breast and nipple changes
  • a need to go to the toilet more often than usual
  • bloating, cramps and backache
  • morning sickness
  • more saliva in your mouth than usual
  • feeling dizzy or fainting
  • feeling tired
  • headaches
  • constipation (when you have 3 or fewer bowel movements in a week) and wind
  • no interest in sex, or wanting to have sex more often.
© RMI Ministry of Health and Human services

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