Third trimester
33 weeks pregnant
The fetus is around the size of a pineapple. Bones are hardening everywhere except the skull, which stays deliberately flexible to allow passage through the birth canal.
Size of
pineapple
Length
43 cm
Weight
1920 g
Your baby at 33 weeks
The skull bones remain unfused and can overlap during birth, a process called moulding. This is why some newborns have oddly shaped heads for a few days.
The immune system is developing, and antibodies pass from you to the fetus, providing protection in the early weeks after birth.
The fetus may have around 2.5 litres of amniotic fluid around it, which begins decreasing from here as the fetus takes up more space.
How you may be feeling
Space is genuinely tight. Movements feel like rolls, stretches and pushes rather than kicks, and you may be able to identify a foot or elbow.
Pelvic pressure increases as the baby sits lower. Many people find walking less comfortable.
Common symptoms around week 33
- Pelvic pressure
- Rolling rather than kicking movements
- Backache
- Swelling
- Difficulty sleeping
Appointments and tests around now
Appointments continue. Group B streptococcus screening is offered in some systems between weeks 35 and 37.
What is normal, and what varies
Movements changing character is expected; movements reducing in amount is not. If you are unsure which is happening, that uncertainty is itself a reason to call.
Worth doing this week
Call if you are unsure about movement
Not knowing whether movement has reduced is a good enough reason. Units expect these calls and would rather check.
Rest on your left where you can
It is commonly recommended for circulation, and many people find it more comfortable as the bump grows.
Discuss group B strep
Practice varies between systems. Ask what your provider does and what happens if it is detected.
Looking ahead
Next week the lungs are nearly mature and the fetus continues putting on weight.
Nearby weeks
Not sure which week you are in? The week tracker works it out from the first day of your last period, and the due date calculator gives you an estimated due date.