Full term foetus. Artwork of a 9 month old foetus in a cutaway uterus. At this stage a normal foetus weighs about 3.4 kilograms and is around 50 cm long from head to rump. The head is in the normal position facing the cervical canal (orange, directly below baby's head). At labour the cervical canal widens up to 10 cm in diameter to allow the baby to pass into the vaginal canal (red, at centre bottom). The placenta (red, at upper left) is attached to the lining of the uterus (orange) and acts, via the umbilical cord (pink coils), as an organ of respiration, nutrition and excretion for the foetus. The foetus is in a clear amniotic sac filled with fluid.