Where do expecting moms get the burst of energy, or "nesting," without sleep?

It is not a mystery that sleeping while pregnant can be difficult. Every person gives the advice of "sleep while you can." Sleep with a newborn is almost nonexistant, but sleep while pregnant is at a minimal too. This can be explained by the physical body changes (not being able to get comfortable), but it can also be explained by mental changes. Many changes are happening to an expecting woman. Her brain structure "gears up" so she can cope with the demands of a newborn. Expecting moms secrete more prolactin, which increases nurturing behavior. (Why some 'sloppy' or 'messy' women are all of a sudden super OCD, and want everything set up NOW, not  later.) New neurons are created in the care taking part of the brain, medial preoptic area. Many pregnant woman have elevated levels of anxiety and hyper awareness. Because of this anxiety, woman may feel energetic and anxious to prepare for their young. Pregnant women are also extremely perceptive. They are able to better read facial expressions, especially fearful and angry expressions, so that they can react quicker to protect their child. Mild to moderate stress levels in mid to late pregnancy has a correlation with better mental and physical outcomes for toddlers.