Your baby's bladder now fills and empties every 30 minutes; she swallows the amniotic fluid, filters it through her kidneys, and then passes it as urine. The bladder volume is tiny at this stage, and even by 32 weeks it will only be 10 ml, reaching 40 ml by 40 weeks. Your baby produces very dilute urine, having only a limited capacity to reabsorb water in the kidney to concentrate the urine. However, the placenta performs most of the kidney functions until birth.
Your baby's blood system can now make and break down blood clots. The placenta has been able to form clots for some time, reducing the risk of bleeding. A small number of white blood cells are now being produced by your baby but she is still relying on yours to fight infection. Her red blood cells contain hemoglobin that transfers oxygen to all the cells of the body. Before birth she has several forms of hemoglobin that differ from yours. These are more stable at a lower acidity and bind more easily to oxygen. This allows your baby's body to extract the oxygen in your hemoglobin for her own use.