Week 37 – 38

Your baby could weigh around 3.1kg (approximately 6 lbs 13 ozs) or more and measure around 48.5 cm from head to toe (about 19 inches). Babies born after 37 weeks are regarded as being ‘on time’ or ‘term’. Babies born before 37 weeks are regarded as premature.

The proportion of fat on your baby’s body has increased from being only 30 grams at 30 weeks, to around 430 grams by the time they are born (approximately 16% of their total body weight).
The fine covering of hair on your baby’s body (called ‘lanugo’) all but disappears by this stage, but they still tend to be covered by the thick, greasy, white cream called ‘vernix’. The testes of most baby boys have now descended from their groin area into their scrotum.

Your baby’s placenta now covers about 1/3 of the inner surface of the uterus and processes around 12 litres of blood per hour (or 600 pints in 24 hours).

Week 35 – 37

At this stage your baby could weigh in the vicinity of 2.6kg (2,600 grams or about 5 lbs 12 ozs) and measure about 47 cm from head to toe (or 18 1/2 inches). Your baby is now in ‘normal’ proportions and is quite plump! Before 36 weeks the head size of unborn babies tends to be larger than their belly size, but at around 36 weeks this equalises. From now on, their belly grows larger than their head!

As your baby’s due date approaches, their overall growth slows down considerably! It is estimated that babies do not grow as much in length now but put on approximately 230 grams per week (or about an ounce a day).

By 36 to 37 weeks your baby’s lungs are fully mature. However, babies of diabetic mothers can have delayed lung maturity until about 38 to 40 weeks.

Week 33 – 34

Your baby now weighs about 2.1kg (2,100 grams or approximately 4 lbs 10 ozs) and measures about 45 cm in length (or 17.75 inches). They are now fully formed physically and have a firm grasp reflex. During the last 6 weeks, your baby’s main task is to gain weight and grow a little larger, as well as build up their immune system, which is obtained from their mother as antibodies passed through the placenta.

Most babies assume a ‘head down’ position around this time and stay this way until they are born. You may notice your baby’s movements changing in character (to be more ‘stretches’ and ‘squirms’) as they grow larger and there is comparatively less room for them to move.
Your baby can now determine the difference between sweet and sour tastes. Premature babies as early as 33 weeks have been observed to suck harder on a teat dipped in glucose! However, unborn babies can also detect subtle changes in the ‘flavour’ of the amniotic fluid surrounding them. It is believed the fluid acts as a type of “flavour bridge” to their mother’s breast milk, which also carries different food flavours from the mother’s diet.


Your baby can swallow up to a litre of amniotic fluid each day, passing this out as a type of ‘urine’ through their kidneys and bladder, back into the fluid around them.

Week 31 – 32

Your baby weighs about 1.7kg (1,700 grams or approximately 3 lbs 12 ozs) and measures about 43 cm from head to toe (or just under 17 inches).

Your baby has now put on enough weight to make them look a little chubby! The fine hair that covered their entire body (called lanugo) now disappears from their face, but remains on their torso. Most babies sleep about 90% of the time at this stage, in between having shorts bursts of movement when awake (every 1 to 2 hours). Many unborn babies like to be active during the evenings when their mother is trying to sleep, between 9pm and 1am!
Your baby’s lungs continue to mature, producing increasing amounts of ‘surfactant’. This is a fatty liquid (called phospholipid) that lines their lungs, keeping them moist and helping the sacs within them (called alveoli) to expand efficiently for breathing. Your baby’s sucking and swallowing action (required to drink milk) fully coordinates between 32 to 34 weeks.

Week 29 – 30

Your baby now weighs about 1,350 grams (approximately 3 lbs) and measures about 40 cm in length (or 15.75 inches).

Your baby’s bones are now mature enough to start producing their own blood supply from their bone marrow, taking over this task from their liver and spleen. During the last 3 months unborn babies begin to store iron in their liver (supplied from their mother’s body). This is Nature’s way of meeting their iron requirements until they start eating solids, about 4 to 6 months after birth.
From week 30 your baby develops a special layer of fat called ‘brown adipose tissue’ (or BAT). This is similar to the kind of fat found in hibernating animals. BAT is your baby’s main source of heat production after birth, because newborn babies have a limited ability to shiver, sweat or move to regulate their own body temperature.

Your baby’s brain is increasing in size and complexity and the pupils of their eyes can now respond to light, allowing your baby to focus more readily and see dim shapes.

Week 27 – 28

Your baby is about 37cm long (or 14.8 inches) and weighs about 1,100 grams (or 2lb 7 oz). Many babies of this gestation like to lie in a breech position.
Your baby is now developing their immune system, as your natural antibodies pass to them through the placenta. They are now capable of starting to coordinate their ‘suck and swallow’ action that will be needed for them to drink milk after being born. However, this reflex is not fully mature until 32 to 34 weeks. Your baby may look around and is capable of distinguishing light from dark and tracking movement.

Week 25 – 26

Your baby measures about 33 cm (or 13.2 inches) and weighs about 800 grams (or 1lb 12 oz). Their eyelids are no longer fused so they can now open them and even blink! It is possible for your baby to respond to bright light (such as shining a torch through the woman’s belly). Newborn babies have vision that is perfectly focussed from about 20 to 30 cm (usually as far away as the face of the person holding them!)

Your baby can now recognise your voice and be noticeably calmed by it (observed by their heart rate slowing). They can also recognise your partner’s voice and different types of music.

Your baby’s movements are generally more regular now and they may physically respond to you if you press on parts of their protruding feet, bottom or hands.

Week 23 – 24

Your baby has grown to be about 28 cm long (or 11.2 inches) and approximately 600 grams in weight (or 1 lb 5 oz).

Your baby now has definite sleep and wake patterns (although they may sleep up to 95% of the time) and now have REM (or rapid eye movement), which indicates they may be dreaming!

Your baby can now rotate their head and could experience hiccups. Hiccups are caused by the sudden, irregular contractions of their immature diaphragm (the muscle that supports their lungs) and while they may be capable of sporadic hiccoughs as early as 12 weeks gestation, they are generally stronger and more rhythmic by this stage. Some unborn babies hiccup quite frequently. This may be sensed by the mother as small, regular ‘jumps’ in their belly every now and then for short periods of time.
Your baby is now covered with a thick layer of white vernix cream to protect their skin in their watery environment and they now have sweat glands. A fine layer of fat is now forming between their muscle tissues and skin. This covers their blood vessels and makes their complexion look less translucent.

Week 21 – 22

Your baby is around 25 cm long from head to toe (or 10 inches) and weighs just under ½ a kilogram (or about 1pound). By 22 weeks, your baby’s nervous system completely ‘connects’. The vital link between their brain and spinal cord (the brain stem) now matures and many nerve cells make vigorous connections. When this happens your baby becomes capable of recognising warmth, light, sound and pain.

Your baby’s skin is increasingly being covered by vernix. A thick, white, greasy cream that protects their skin in their watery environment. This disappears by 40 weeks (or if your baby is born more than a week early, you will notice it is still on their skin). Your baby’s eyelids are still fused shut but the retinas of their eyes are fully developed and they now have distinct eyelashes and eyebrows. Your baby’s hair follicles are now pigmenting to give your baby’s hair colour, looking either dark, fair or red.

Babies at this stage typically like to lie in a transverse position (or crossways), with their feet and bottom on one side of your belly and their head on the other side (rather than head down).

Week 19 – 20

Week 20 is seen as the ‘half way’ point in a standard 40 week pregnancy. Your baby now measures about 22 cm from head to toe (or 8.8 inches) and weighs about 340 grams (or 12 ounces).

During the 20th week, your baby’s nails form and their fingerprints are now visibly engraved in their fine skin. Their permanent teeth now appear behind their baby teeth deep within their gums. The bones in your baby’s inner ear and their nerve endings are now developed to the point where it is possible for them to hear sounds (although their ears are not structurally complete until 24 weeks).

Week 17 – 18

Your baby measures about 19 cm long from head to toe (or 7.6 inches) and weighs about 280 grams (9.8 ounces).

Your baby’s skin is still fine, transparent and slightly wrinkled because they do not have a layer of fat yet. The many blood vessels flowing underneath their skin makes it appear purply-red. The scant whiskers of hair on various parts of your baby’s body have now become a fine layer of down covering them all over (called ‘lanugo’). This hair helps protect your baby’s skin and is only shed a few weeks before they are due to be born.

Your baby will now explore their own body with their hands and if you are having twins or more they may try and locate each other, by touching and exploring the body of their brother or sister. There is plenty of fluid around your baby at this stage, allowing them to turn, twist and change position frequently.

Week 15 – 16

Your baby has grown to around 15 cms in length (or 6 inches) from head to toe, or about 10cms (or 4 inches) from ‘crown to rump’. They probably weigh about 120 grams (or 4.2 ounces) and are more in proportion physically, but their head still accounts for about 1/3 of their body.

Your baby’s vocal chords are now formed and they now make different facial expressions. They can grasp with their hands and suck their thumb and may explore the inside of your uterus with their hands. If your uterus is pressed from the outside, this may produce a small startle response in your baby.

The amniotic fluid increases around your baby, so they move freely, floating like an astronaut in space and their umbilical cord is now completely mature. The cord contains two arteries and one vein, enclosed and protected by a thick gristle-like substance called ‘Wharton’s Jelly’. This makes the cord slippery and allows it to move freely around your baby and avoid compression.

Your baby is now bigger than their placenta, but you could still cradle them in one hand.

Week 13 – 14

Your baby is now 9 cm long (or 3.6 inches) and weighs approximately 50 grams (or 1.75 ounces). Many women notice a renewed burst of energy by this stage, but may feel concerned because they do not experience as many obvious signs of pregnancy (and it is too early to feel the reassuring movements of their baby yet). You may need to loosen the clothing around your waistline now, but at this stage many women say they feel they just look ‘fat’, rather than pregnant! From here on in, your baby will grow quite rapidly and in the coming weeks your belly will quickly ‘pop out’!

Your baby’s body now grows more rapidly than their head.

Your baby now has a gag reflex and their nose and nasal passages are fully developed.

Week 12

This marks the end of the 1st trimester (or the first 3 months of pregnancy) and the beginning of the 2nd trimester (the second 3 months of pregnancy).

It has now been 70 days since your baby was conceived and they measure about 7.6 cm (or 3.04 inches) and weigh approximately 30 grams (about 1 ounce). As your uterus grows upwards and out of the bones of your pelvis, the pressure is taken off your bladder and your waistline may start to thicken.

Your baby’s bones are now changing from being soft and flexible (made of cartilage) to being more hardened, as the centre of them ‘ossifies’. Your baby is now capable of making creeping and climbing movements, although for most women their baby is still too small to be aware of them. Very fine whiskers of hair start to appear on your baby’s upper lips and eyebrows.

The placenta is now fully functional but remains larger in size than the baby (until about 16 weeks). The placenta supplies your baby with oxygen, fats, proteins, vitamins and minerals as well as removing carbon dioxide and waste materials, by ‘filtering’ or ‘sieving’ them through the placental tissues attached to the uterus. This intricate process is called ‘diffusion’ and the exchange is possible because the blood vessels of the mother and baby are incredibly close together, yet remarkably always stay separate.

Your baby’s bowels are now able to expand and contract (called ‘peristalsis’) and from now on they start filling with a black-green, tar-like substance that will be their first bowel motion passed after the birth, called ‘meconium’.

Week 11

Your baby is now around 5 cm long (or 2 inches) from crown to rump and weighing about 8 grams (or 0.28 ounces). Nearly doubling in size during the last week! By the end of this week your uterus will grow up out of the bones of your pelvis.

Your baby now has the early components of sucking and swallowing (although not mature until 24 to 28 weeks) and their taste buds are mature enough to taste the amniotic fluid that surrounds them. Your baby’s kidneys are now functioning and secreting fluid into their bladder. Fluid they will soon pass as a type of ‘urine’ into the amniotic fluid. This cycle of swallowing and urinating amniotic fluid continues up until birth.