Your amazing baby can do so many things already, including being able to open his mouth and yawn, hiccup, and swallow. Swallowing develops earlier than sucking. Your baby will be swallowing the amniotic fluid regularly but the more complex sucking movements cannot be identified until 18-20 weeks. Swallowing will encourage gut development. The amniotic fluid enters into the stomach not the lungs, which are protected now by the vocal cords and the higher pressure of the lung's own fluid. The amniotic fluid will later be excreted as urine when the fetal kidneys start to function.
After the stomach, the amniotic fluid will enter the small bowel. The intestinal walls are developing muscular layers but these do not yet contract in a coordinated way to move the fluid along the digestive tract. It will be 20 weeks before the structural organization of the gut is finally complete. Many digestive enzymes are starting to be released into the gut but these currently act as a stimulus to development rather than for the absorption of nutrients.
Your baby is reliant on a steady stream of glucose, which is stored as glycogen in the liver. This continues throughout pregnancy and at birth your baby will, for her size, have significantly larger glycogen reserves than adults do. The correct level of glucose is controlled by insulin secreted by the pancreas. The placenta, however, has little control over the amount it takes from your blood-stream and passes on. For this reason if your glucose level is very high, for example in poorly controlled diabetes, the baby will be presented with high levels of glucose. He will maintain a normal glucose level but the insulin released leads to increased fat deposition and weight gain.