At week 33, your little one is now over 4 pounds and as long as a stalk of celery! Given baby's ever-increasing size, it is likely your amniotic fluid has hit its max point and your womb is more baby than fluid now which can make those kicks and jabs feel more significant and stronger than ever before. Baby is also starting to develop her immune system soon and is reaping the benefits of passing antibodies from your body to hers as she prepares the system that will help her fight off infection and communicable illness on the outside.
Baby is also still practicing her breathing so she will be a pro at using her lungs and making the rhythmic movement necessary for breathing by the time she emerges into the world. Her pupils with now dilate in response to light that filters in through the thinning walls of the abdomen and uterus. Most importantly perhaps is that the baby's brain is now almost fully developed and with it a functional nervous system. This new development means the baby is ready to learn new skills and execute more intricate movement patterns. Your baby may practice movements like thumb sucking, breathing, and reflexes that increase coordination.
The womb creates a small and snug environment where baby can feel secure and reflex jerking is limited to avoid waking a restful baby or causing anxiety. Once your baby is born, a good swaddle can offer the same sensations and help baby relax by providing an environment similar to the one she is used to from the womb.
- American Pregnancy Association - Week 33