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Fetal Development in the Third Trimester

August 10, 2013 by HealthyFamilies BC

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pregnant woman walking with her family



During the third trimester (the last three months of pregnancy) your baby continues to develop, gains weight and begins to prepare for the birthing process.  

Here's a detailed overview of how your baby’s growing.

Full term babies are best able to cope with birth and life outside the uterus. The earlier a baby is born, the greater the need for special care to decrease risks from a preterm birth.

28 weeks: 35–37 cm (14 in.) 1100 g (2 lb. 5 oz.)






Your developing baby’s body is still lean but the skin is less wrinkled and red.

The body can now store iron, calcium, and other nutrients. Your baby can also hear and respond to sounds.



32 weeks: 40–42 cm (16 in.) 1800–2100 g (4 lb.–4 lb. 7 oz.)

Your baby’s skin is pink and smoothing out as the fat forms under it. Your baby develops a sense of taste and becomes aware of sounds outside your body. If the baby is male, the testicles begin to drop into the scrotum. The pupils in the baby’s eyes can react to light.


36 weeks: 45–47 cm (18 in.) 2200–2900 g (4 lb. 11 oz.–6 lb. 5 oz.)

Your baby’s body is rounded and usually plump. The downy hair on the body begins to disappear. The skin is smooth, pink, and covered with a grayish white, cheese like substance called vernix. The baby continues to increase the store of antibodies and is able to resist some diseases. Usually your baby can safely be born at this age.


40 weeks: 45–55 cm (18–22 in.) 3200 g + (7 lb.+)

Head hair is usually present. The testicles of male babies are now in the scrotum, and the labia majora of female babies are developed.

Your baby is now full term!


40 – 42 weeks (post dates): weight will increase

The fontanels (soft spots on the head) are becoming smaller and the skull bones are growing firmer and less flexible. The skin may become looser as the fat layer decreases. Skin is also drier and may have small cracks as the amount of vernix decreases. Nails may be long.


More than 42 weeks(overdue): weight will increase
The skin continues to dry and will have cracks as the amount of vernix continues to decrease.


Resources & Links:

HealthLink BC: Interactive Tool: From Embryo to Baby in 9 Months
HealthLink BC: Baby Development

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