During week 31 of your pregnancy, the baby’s reproductive system continues to develop. If your baby is a boy, his testicles are moving from their location near the kidneys through the groin on their way into the scrotum. If your baby is a girl, her clitoris is now relatively prominent. However, the labia are still small and don't yet cover it.
Your baby's lungs are now more developed, but they're not yet fully mature. If your baby is born this week, he or she will probably need to stay six weeks or more in a neonatal intensive care unit (NICU) and will need the help of a ventilator to breathe. However because your baby's brain is more mature than it was several weeks ago, he or she will be at reduced risk of having bleeding in the brain.
Breathlessness may be more of a problem now, especially if you overdo things. Try to get as much rest as possible and slow down any exercise regime to a pace that suits you. If your breasts feel uncomfortable when you go to bed, wear a maternity or specially designed sleep bra at night.
The organs are almost completely developed, apart from the lungs which are still not fully mature. The brain is still growing and the nerve cells and connections are now working. The baby is around 16.2 inches (41 cm) long and weighs about 3.3 pounds (1,5 kg).