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Weeks 39-40

Weeks 39-40


You are now 39 weeks pregnant, which is the beginning of week 40. At term, the average weight a baby born in Australia is about 3,300 grams (or 7lb 41/2oz), but this can range from 2,800grams to 4,500grams (6lb 3oz to 9lb 15oz). The average length is about 50 cms (or 20 inches) from head to toe, but this can range from 46 to 56 cms (or 18 to 22 inches). A baby's head circumference is also measured and averages around 35 cms, but can range from 33 to 37 cms! 

FetalDevelopmentWeek39-(2).jpg

By 40 weeks your baby is assumed to be 'cooked' to perfection! Most of the vernix on their skin has gone, but there may be remnants of it in their armpits and groin areas. Their fingernails look long and their skin is supple. Only about 5% of babies are born on their actual 'due date', with most babies coming within a week after the day estimated! 

Your baby's 'breathing exercises' are believed to naturally stop about 24 to 48 hours before the labour commences. Unborn babies hold about 75 to 100mls of amniotic fluid in their lungs (or about 25 mls per kg of body weight). During the labour, hormones are released by the mother, triggering the baby's system to start absorbing fluid from their lungs into their blood stream before birth. A small amount of fluid normally remains in the baby's lungs after being born and is fully absorbed within 24 hours (this is why many newborn babies sound a little 'gurgly' when they breathe during the first few hours after birth). 

If the woman does not experience labour before her baby's birth (i.e. an elective Caesarean) the baby has an increased chance of being born with more fluid in their lungs, possibly inhibiting their breathing, a condition called 'wet lung'.

Go to Weeks 41 - 42

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